[Solved] Websocket error after upgrade to 7.8.9

[Anette]

Okey found the solution here

Mattermost reports Please check connection, Mattermost unreachable. If issue persists, ask administrator to check WebSocket port

The important upgrade notes gives tips on this Important Upgrade Notes — Mattermost documentation. One of the notes mentions about setting the AllowCorsFrom to “*” in mattermost/config/config.json.