Api Login error. /api/v4/users/login

I’m using API method /api/v4/users/login. When i send login_id’ and ‘password’ from my computer - i resive token and all ok. But when i send reqest from remote web server it resive ‘null’.

In mattermoset “Server Logs” i find errors
“websocket: the client is not using the websocket protocol: ‘upgrade’ token not found in ‘Connection’ header” "

I’m not using websockets in API. What this arror is meen??