WebSocket connection to failed(wss)

■Environment in development
The configuration of the server that we are currently building is as follows.

【User Computer】 -https- 【Load balancer】-http- 【Nginx server】-http- 【Mattermost server】 -http- 【Database server】

■Current Issues
If you check in the developer tools of chrome, you will see the following.
How do I configure Nginx to work properly?

■configuration file
filename:/etc/nginx/conf.d/mattermost

upstream backend {
   server [Mattermost server IP]:8065;
   keepalive 32;
}
proxy_cache_path /var/cache/nginx levels=1:2 keys_zone=mattermost_cache:10m max_size=3g inactive=120m use_temp_path=off;

server {
    listen 80;
    server_name [Mattermost server FQDN];

    location ~ /api/v[0-9]+/(users/)?websocket$ {
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "upgrade";
        client_max_body_size 50M;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
        proxy_set_header X-Frame-Options SAMEORIGIN;
        proxy_buffers 256 16k;
        proxy_buffer_size 16k;
        client_body_timeout 60;
        send_timeout 300;
        lingering_timeout 5;
        proxy_connect_timeout 90;
        proxy_send_timeout 300;
        proxy_read_timeout 90s;
        proxy_pass http://backend;
    }

    location / {
        client_max_body_size 50M;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "upgrade";
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
        proxy_set_header X-Frame-Options SAMEORIGIN;
        proxy_buffers 256 16k;
        proxy_buffer_size 16k;
        proxy_read_timeout 600s;
        proxy_cache mattermost_cache;
        proxy_cache_revalidate on;
        proxy_cache_min_uses 2;
        proxy_cache_use_stale timeout;
        proxy_cache_lock on;
        proxy_http_version 1.1;
        proxy_pass http://backend;
    }
}

/opt/mattermost/config/config.json

{
    "ServiceSettings": {
        "SiteURL": "https://[mattermost server FQDN]",
        "WebsocketURL": "",
        "LicenseFileLocation": "",
        "ListenAddress": ":8065",
        "ConnectionSecurity": "",
        "TLSCertFile": "",
        "TLSKeyFile": "",
        "TLSMinVer": "1.2",
        "TLSStrictTransport": false,
        "TLSStrictTransportMaxAge": 63072000,
        "TLSOverwriteCiphers": [],
        "UseLetsEncrypt": false,
        "LetsEncryptCertificateCacheFile": "./config/letsencrypt.cache",
        "Forward80To443": false,
        "TrustedProxyIPHeader": [
            "X-Forwarded-For",
            "X-Real-Ip"
        ],
        "ReadTimeout": 300,
        "WriteTimeout": 300,
        "IdleTimeout": 60,
        "MaximumLoginAttempts": 10,
        "GoroutineHealthThreshold": -1,
        "EnableOAuthServiceProvider": false,
        "EnableIncomingWebhooks": true,
        "EnableOutgoingWebhooks": true,
        "EnableCommands": true,
        "EnablePostUsernameOverride": false,
        "EnablePostIconOverride": false,
        "GoogleDeveloperKey": "",
        "EnableOnlyAdminIntegrations": true,
        "EnableLinkPreviews": true,
        "RestrictLinkPreviews": "",
        "EnableTesting": false,
        "EnableDeveloper": false,
        "EnableOpenTracing": false,
        "EnableSecurityFixAlert": true,
        "EnableInsecureOutgoingConnections": false,
        "AllowedUntrustedInternalConnections": "",
        "EnableMultifactorAuthentication": false,
        "EnforceMultifactorAuthentication": false,
        "EnableUserAccessTokens": false,
        "AllowCorsFrom": "*",
        "CorsExposedHeaders": "",
        "CorsAllowCredentials": false,
        "CorsDebug": false,
        "AllowCookiesForSubdomains": false,
        "ExtendSessionLengthWithActivity": true,
        "SessionLengthWebInDays": 30,
        "SessionLengthMobileInDays": 30,
        "SessionLengthSSOInDays": 1,
        "SessionCacheInMinutes": 10,
        "SessionIdleTimeoutInMinutes": 43200,
        "WebsocketSecurePort": 443,
        "WebsocketPort": 80,
        "WebserverMode": "gzip",
        "EnableGifPicker": true,
        "GfycatApiKey": "2_KtH_W5",
        "GfycatApiSecret": "3wLVZPiswc3DnaiaFoLkDvB4X0IV6CpMkj4tf2inJRsBY6-FnkT08zGmppWFgeof",
        "EnableCustomEmoji": true,
        "EnableEmojiPicker": true,
        "RestrictCustomEmojiCreation": "all",
        "RestrictPostDelete": "all",
        "AllowEditPost": "always",
        "PostEditTimeLimit": -1,
        "TimeBetweenUserTypingUpdatesMilliseconds": 5000,
        "EnablePostSearch": true,
        "EnableFileSearch": true,
        "MinimumHashtagLength": 3,
        "EnableUserTypingMessages": true,
        "EnableChannelViewedMessages": true,
        "EnableUserStatuses": true,
        "ExperimentalEnableAuthenticationTransfer": true,
        "ClusterLogTimeoutMilliseconds": 2000,
        "CloseUnusedDirectMessages": false,
        "EnablePreviewFeatures": true,
        "EnableTutorial": true,
        "ExperimentalEnableDefaultChannelLeaveJoinMessages": true,
        "ExperimentalGroupUnreadChannels": "disabled",
        "ExperimentalChannelOrganization": false,
        "ImageProxyType": "",
        "ImageProxyURL": "",
        "ImageProxyOptions": "",
        "EnableAPITeamDeletion": false,
        "EnableAPIUserDeletion": false,
        "ExperimentalEnableHardenedMode": false,
        "DisableLegacyMFA": true,
        "ExperimentalStrictCSRFEnforcement": false,
        "EnableEmailInvitations": false,
        "DisableBotsWhenOwnerIsDeactivated": true,
        "EnableBotAccountCreation": false,
        "EnableSVGs": false,
        "EnableLatex": false,
        "EnableAPIChannelDeletion": false,
        "EnableLocalMode": false,
        "LocalModeSocketLocation": "/var/tmp/mattermost_local.socket",
        "EnableAWSMetering": false,
        "SplitKey": "",
        "FeatureFlagSyncIntervalSeconds": 30,
        "DebugSplit": false,
        "ThreadAutoFollow": true,
        "CollapsedThreads": "disabled",
        "ManagedResourcePaths": "",
        "EnableLegacySidebar": false,
        "EnableReliableWebSockets": true
    },
    "TeamSettings": {
        "SiteName": "mattermost",
        "MaxUsersPerTeam": 10000,
        "EnableTeamCreation": true,
        "EnableUserCreation": true,
        "EnableOpenServer": false,
        "EnableUserDeactivation": false,
        "RestrictCreationToDomains": "",
        "EnableCustomUserStatuses": true,
        "EnableCustomBrand": false,
        "CustomBrandText": "",
        "CustomDescriptionText": "",
        "RestrictDirectMessage": "any",
        "RestrictTeamInvite": "all",
        "RestrictPublicChannelManagement": "all",
        "RestrictPrivateChannelManagement": "all",
        "RestrictPublicChannelCreation": "all",
        "RestrictPrivateChannelCreation": "all",
        "RestrictPublicChannelDeletion": "all",
        "RestrictPrivateChannelDeletion": "all",
        "RestrictPrivateChannelManageMembers": "all",
        "EnableXToLeaveChannelsFromLHS": false,
        "UserStatusAwayTimeout": 300,
        "MaxChannelsPerTeam": 2000,
        "MaxNotificationsPerChannel": 1000000,
        "EnableConfirmNotificationsToChannel": true,
        "TeammateNameDisplay": "username",
        "ExperimentalViewArchivedChannels": false,
        "ExperimentalEnableAutomaticReplies": false,
        "ExperimentalHideTownSquareinLHS": false,
        "ExperimentalTownSquareIsReadOnly": false,
        "LockTeammateNameDisplay": false,
        "ExperimentalPrimaryTeam": "",
        "ExperimentalDefaultChannels": []
    },
    "ClientRequirements": {
        "AndroidLatestVersion": "",
        "AndroidMinVersion": "",
        "DesktopLatestVersion": "",
        "DesktopMinVersion": "",
        "IosLatestVersion": "",
        "IosMinVersion": ""
    },
    "SqlSettings": {
        "DriverName": "postgres",
        "DataSource": "postgres://mmuser:[PW]@[DB serverIP]:5432/mattermost?sslmode=disable\u0026connect_timeout=10",
        "DataSourceReplicas": [],
        "DataSourceSearchReplicas": [],
        "MaxIdleConns": 20,
        "ConnMaxLifetimeMilliseconds": 3600000,
        "ConnMaxIdleTimeMilliseconds": 300000,
        "MaxOpenConns": 300,
        "Trace": false,
        "AtRestEncryptKey": "m8t37obsnpcud6jdkrzp5ficunieug91",
        "QueryTimeout": 30,
        "DisableDatabaseSearch": false,
        "ReplicaLagSettings": []
    },
    "LogSettings": {
        "EnableConsole": false,
        "ConsoleLevel": "INFO",
        "ConsoleJson": false,
        "EnableColor": false,
        "EnableFile": true,
        "FileLevel": "INFO",
        "FileJson": true,
        "FileLocation": "",
        "EnableWebhookDebugging": true,
        "EnableDiagnostics": false,
        "EnableSentry": true,
        "AdvancedLoggingConfig": ""
    },
    "ExperimentalAuditSettings": {
        "FileEnabled": false,
        "FileName": "",
        "FileMaxSizeMB": 100,
        "FileMaxAgeDays": 0,
        "FileMaxBackups": 0,
        "FileCompress": false,
        "FileMaxQueueSize": 1000,
        "AdvancedLoggingConfig": ""
    },
    "NotificationLogSettings": {
        "EnableConsole": true,
        "ConsoleLevel": "INFO",
        "ConsoleJson": true,
        "EnableColor": false,
        "EnableFile": true,
        "FileLevel": "INFO",
        "FileJson": true,
        "FileLocation": "",
        "AdvancedLoggingConfig": ""
    },
    "PasswordSettings": {
        "MinimumLength": 10,
        "Lowercase": true,
        "Number": true,
        "Uppercase": true,
        "Symbol": true
    },
    "FileSettings": {
        "EnableFileAttachments": true,
        "EnableMobileUpload": true,
        "EnableMobileDownload": true,
        "MaxFileSize": 10485760,
        "DriverName": "local",
        "Directory": "/opt/mattermost/data/",
        "EnablePublicLink": false,
        "ExtractContent": true,
        "ArchiveRecursion": false,
        "PublicLinkSalt": "c8m43np7r6wgauf3n4ng8y1ffphpnesf",
        "InitialFont": "nunito-bold.ttf",
        "AmazonS3AccessKeyId": "",
        "AmazonS3SecretAccessKey": "",
        "AmazonS3Bucket": "",
        "AmazonS3PathPrefix": "",
        "AmazonS3Region": "",
        "AmazonS3Endpoint": "s3.amazonaws.com",
        "AmazonS3SSL": false,
        "AmazonS3SignV2": false,
        "AmazonS3SSE": false,
        "AmazonS3Trace": false
    },
    "EmailSettings": {
        "EnableSignUpWithEmail": false,
        "EnableSignInWithEmail": true,
        "EnableSignInWithUsername": true,
        "SendEmailNotifications": false,
        "UseChannelInEmailNotifications": false,
        "RequireEmailVerification": false,
        "FeedbackName": "",
        "FeedbackEmail": "",
        "ReplyToAddress": "",
        "FeedbackOrganization": "",
        "EnableSMTPAuth": false,
        "SMTPUsername": "",
        "SMTPPassword": "",
        "SMTPServer": "150.26.199.247",
        "SMTPPort": "25",
        "SMTPServerTimeout": 10,
        "ConnectionSecurity": "",
        "SendPushNotifications": true,
        "PushNotificationServer": "https://push-test.mattermost.com",
        "PushNotificationContents": "full",
        "PushNotificationBuffer": 1000,
        "EnableEmailBatching": false,
        "EmailBatchingBufferSize": 256,
        "EmailBatchingInterval": 30,
        "EnablePreviewModeBanner": true,
        "SkipServerCertificateVerification": false,
        "EmailNotificationContentsType": "full",
        "LoginButtonColor": "#0000",
        "LoginButtonBorderColor": "#2389D7",
        "LoginButtonTextColor": "#2389D7"
    },
    "RateLimitSettings": {
        "Enable": false,
        "PerSec": 10,
        "MaxBurst": 100,
        "MemoryStoreSize": 10000,
        "VaryByRemoteAddr": true,
        "VaryByUser": false,
        "VaryByHeader": ""
    },
    "PrivacySettings": {
        "ShowEmailAddress": false,
        "ShowFullName": true
    },
    "SupportSettings": {
        "TermsOfServiceLink": "https://mattermost.com/terms-of-service/",
        "PrivacyPolicyLink": "",
        "AboutLink": "",
        "HelpLink": "",
        "ReportAProblemLink": "",
        "SupportEmail": "",
        "CustomTermsOfServiceEnabled": false,
        "CustomTermsOfServiceReAcceptancePeriod": 365,
        "EnableAskCommunityLink": false
    },
    "AnnouncementSettings": {
        "EnableBanner": false,
        "BannerText": "",
        "BannerColor": "#f2a93b",
        "BannerTextColor": "#333333",
        "AllowBannerDismissal": true,
        "AdminNoticesEnabled": true,
        "UserNoticesEnabled": false,
        "NoticesURL": "https://notices.mattermost.com/",
        "NoticesFetchFrequency": 3600,
        "NoticesSkipCache": false
    },
    "ThemeSettings": {
        "EnableThemeSelection": true,
        "DefaultTheme": "default",
        "AllowCustomThemes": true,
        "AllowedThemes": []
    },
    "GitLabSettings": {
        "Enable": true,
        "Secret": "",
        "Id": "",
        "Scope": "",
        "AuthEndpoint": "",
        "TokenEndpoint": "",
        "UserApiEndpoint": "",
        "DiscoveryEndpoint": "",
        "ButtonText": "",
        "ButtonColor": ""
    },
    "GoogleSettings": {
        "Enable": false,
        "Secret": "",
        "Id": "",
        "Scope": "profile email",
        "AuthEndpoint": "https://accounts.google.com/o/oauth2/v2/auth",
        "TokenEndpoint": "https://www.googleapis.com/oauth2/v4/token",
        "UserApiEndpoint": "https://people.googleapis.com/v1/people/me?personFields=names,emailAddresses,nicknames,metadata",
        "DiscoveryEndpoint": "",
        "ButtonText": "",
        "ButtonColor": ""
    },
    "Office365Settings": {
        "Enable": false,
        "Secret": "",
        "Id": "",
        "Scope": "User.Read",
        "AuthEndpoint": "https://login.microsoftonline.com/common/oauth2/v2.0/authorize",
        "TokenEndpoint": "https://login.microsoftonline.com/common/oauth2/v2.0/token",
        "UserApiEndpoint": "https://graph.microsoft.com/v1.0/me",
        "DiscoveryEndpoint": "",
        "DirectoryId": ""
    },
    "OpenIdSettings": {
        "Enable": false,
        "Secret": "",
        "Id": "",
        "Scope": "profile openid email",
        "AuthEndpoint": "",
        "TokenEndpoint": "",
        "UserApiEndpoint": "",
        "DiscoveryEndpoint": "",
        "ButtonText": "",
        "ButtonColor": "#145DBF"
    },
    "LdapSettings": {
        "Enable": false,
        "EnableSync": false,
        "LdapServer": "",
        "LdapPort": 389,
        "ConnectionSecurity": "",
        "BaseDN": "",
        "BindUsername": "",
        "BindPassword": "",
        "UserFilter": "",
        "GroupFilter": "",
        "GuestFilter": "",
        "EnableAdminFilter": false,
        "AdminFilter": "",
        "GroupDisplayNameAttribute": "",
        "GroupIdAttribute": "",
        "FirstNameAttribute": "",
        "LastNameAttribute": "",
        "EmailAttribute": "",
        "UsernameAttribute": "",
        "NicknameAttribute": "",
        "IdAttribute": "",
        "PositionAttribute": "",
        "LoginIdAttribute": "",
        "PictureAttribute": "",
        "SyncIntervalMinutes": 60,
        "SkipCertificateVerification": false,
        "PublicCertificateFile": "",
        "PrivateKeyFile": "",
        "QueryTimeout": 60,
        "MaxPageSize": 0,
        "LoginFieldName": "",
        "LoginButtonColor": "#0000",
        "LoginButtonBorderColor": "#2389D7",
        "LoginButtonTextColor": "#2389D7",
        "Trace": false
    },
    "ComplianceSettings": {
        "Enable": false,
        "Directory": "./data/",
        "EnableDaily": false,
        "BatchSize": 30000
    },
    "LocalizationSettings": {
        "DefaultServerLocale": "en",
        "DefaultClientLocale": "ja",
        "AvailableLocales": ""
    },
    "SamlSettings": {
        "Enable": false,
        "EnableSyncWithLdap": false,
        "EnableSyncWithLdapIncludeAuth": false,
        "IgnoreGuestsLdapSync": false,
        "Verify": true,
        "Encrypt": true,
        "SignRequest": false,
        "IdpUrl": "",
        "IdpDescriptorUrl": "",
        "IdpMetadataUrl": "",
        "ServiceProviderIdentifier": "",
        "AssertionConsumerServiceURL": "",
        "SignatureAlgorithm": "RSAwithSHA1",
        "CanonicalAlgorithm": "Canonical1.0",
        "ScopingIDPProviderId": "",
        "ScopingIDPName": "",
        "IdpCertificateFile": "",
        "PublicCertificateFile": "",
        "PrivateKeyFile": "",
        "IdAttribute": "",
        "GuestAttribute": "",
        "EnableAdminAttribute": false,
        "AdminAttribute": "",
        "FirstNameAttribute": "",
        "LastNameAttribute": "",
        "EmailAttribute": "",
        "UsernameAttribute": "",
        "NicknameAttribute": "",
        "LocaleAttribute": "",
        "PositionAttribute": "",
        "LoginButtonText": "SAML",
        "LoginButtonColor": "#34a28b",
        "LoginButtonBorderColor": "#2389D7",
        "LoginButtonTextColor": "#ffffff"
    },
    "NativeAppSettings": {
        "AppCustomURLSchemes": [
            "mmauth://",
            "mmauthbeta://"
        ],
        "AppDownloadLink": "",
        "AndroidAppDownloadLink": "",
        "IosAppDownloadLink": ""
    },
    "ClusterSettings": {
        "Enable": false,
        "ClusterName": "",
        "OverrideHostname": "",
        "NetworkInterface": "",
        "BindAddress": "",
        "AdvertiseAddress": "",
        "UseIpAddress": true,
        "UseExperimentalGossip": true,
        "EnableGossipCompression": true,
        "EnableExperimentalGossipEncryption": false,
        "ReadOnlyConfig": true,
        "GossipPort": 8074,
        "StreamingPort": 8075,
        "MaxIdleConns": 100,
        "MaxIdleConnsPerHost": 128,
        "IdleConnTimeoutMilliseconds": 90000
    },
    "MetricsSettings": {
        "Enable": false,
        "BlockProfileRate": 0,
        "ListenAddress": ":8067"
    },
    "ExperimentalSettings": {
        "ClientSideCertEnable": false,
        "ClientSideCertCheck": "secondary",
        "EnableClickToReply": false,
        "LinkMetadataTimeoutMilliseconds": 5000,
        "RestrictSystemAdmin": false,
        "UseNewSAMLLibrary": false,
        "CloudUserLimit": 0,
        "CloudBilling": false,
        "EnableSharedChannels": false,
        "EnableRemoteClusterService": false
    },
    "AnalyticsSettings": {
        "MaxUsersForStatistics": 2500
    },
    "ElasticsearchSettings": {
        "ConnectionUrl": "http://localhost:9200",
        "Username": "elastic",
        "Password": "changeme",
        "EnableIndexing": false,
        "EnableSearching": false,
        "EnableAutocomplete": false,
        "Sniff": true,
        "PostIndexReplicas": 1,
        "PostIndexShards": 1,
        "ChannelIndexReplicas": 1,
        "ChannelIndexShards": 1,
        "UserIndexReplicas": 1,
        "UserIndexShards": 1,
        "AggregatePostsAfterDays": 365,
        "PostsAggregatorJobStartTime": "03:00",
        "IndexPrefix": "",
        "LiveIndexingBatchSize": 1,
        "BulkIndexingTimeWindowSeconds": 3600,
        "RequestTimeoutSeconds": 30,
        "SkipTLSVerification": false,
        "Trace": ""
    },
    "BleveSettings": {
        "IndexDir": "",
        "EnableIndexing": false,
        "EnableSearching": false,
        "EnableAutocomplete": false,
        "BulkIndexingTimeWindowSeconds": 3600
    },
    "DataRetentionSettings": {
        "EnableMessageDeletion": false,
        "EnableFileDeletion": false,
        "MessageRetentionDays": 365,
        "FileRetentionDays": 365,
        "DeletionJobStartTime": "02:00",
        "BatchSize": 3000
    },
    "MessageExportSettings": {
        "EnableExport": false,
        "ExportFormat": "actiance",
        "DailyRunTime": "01:00",
        "ExportFromTimestamp": 0,
        "BatchSize": 10000,
        "DownloadExportResults": false,
        "GlobalRelaySettings": {
            "CustomerType": "A9",
            "SmtpUsername": "",
            "SmtpPassword": "",
            "EmailAddress": "",
            "SMTPServerTimeout": 1800
        }
    },
    "JobSettings": {
        "RunJobs": true,
        "RunScheduler": true
    },
    "PluginSettings": {
        "Enable": true,
        "EnableUploads": false,
        "AllowInsecureDownloadUrl": false,
        "EnableHealthCheck": true,
        "Directory": "./plugins",
        "ClientDirectory": "./client/plugins",
        "Plugins": {
            "com.mattermost.plugin-incident-management": {
                "BotUserID": "7gcec9fhm7bqudinetimaxs17o"
            }
        },
        "PluginStates": {
            "com.mattermost.nps": {
                "Enable": true
            },
            "com.mattermost.plugin-channel-export": {
                "Enable": true
            },
            "com.mattermost.plugin-incident-management": {
                "Enable": true
            }
        },
        "EnableMarketplace": true,
        "EnableRemoteMarketplace": true,
        "AutomaticPrepackagedPlugins": true,
        "RequirePluginSignature": false,
        "MarketplaceUrl": "https://api.integrations.mattermost.com",
        "SignaturePublicKeyFiles": [],
        "ChimeraOAuthProxyUrl": ""
    },
    "DisplaySettings": {
        "CustomUrlSchemes": [],
        "ExperimentalTimezone": true
    },
    "GuestAccountsSettings": {
        "Enable": false,
        "AllowEmailAccounts": true,
        "EnforceMultifactorAuthentication": false,
        "RestrictCreationToDomains": ""
    },
    "ImageProxySettings": {
        "Enable": false,
        "ImageProxyType": "local",
        "RemoteImageProxyURL": "",
        "RemoteImageProxyOptions": ""
    },
    "CloudSettings": {
        "CWSUrl": "https://customers.mattermost.com",
        "CWSAPIUrl": "https://portal.internal.prod.cloud.mattermost.com"
    },
    "ImportSettings": {
        "Directory": "./import",
        "RetentionDays": 30
    },
    "ExportSettings": {
        "Directory": "./export",
        "RetentionDays": 30
    }
}

I’m sorry my English is not good.
Please help me.