What can go wrong for LiveQuery when start using HTTPS (indeed it was nginx)?

Parse Server 📡
#1

On local and stage servers with HTTP LiveQuery work fine. But on prod server don’t work functionality based on it and I don’t see some lines in logs that point LiveQuery is working.
When the first client after start connect on HTTP I could see:

    info: Parse LiveQuery Server starts running

    info: Create new client: xxx-xxx-....

On prod (HTTPS) only

    info: Parse LiveQuery Server starts running

No info about connect, nor about disconnect.

Use only 2 settings for LiveQuery

"liveQuery": {
    "classNames": ["xxx", "xxx", "xxx"]
  },
 "startLiveQueryServer": "true"

and both are the same for all servers.

I don’t think that something with parse server, rather outer reasons, but what it could be?..

UPD. When try to connect via LiveQueryClient I have got error:

e =  Event {
  "isTrusted": false,
  "message": "Expected HTTP 101 response but was '403 Forbidden'",
}

UPD2. I was advised to read this, becouse our server use nginx.

Parse Server Livequery Error in localhost
#3

In the end it turned out that does not matter - HTTP or HTTPS - the new impotant element become nginx. Changing protocol to HTTPS was just a coincidence. Everything had to be revealed on stage server but there still simple setup without proxy.

All was solved by adding two lines to nginx config:

    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection "upgrade";

in according with abovementioned manual or analogical article.

But I don’t understand may be the second example from there (more complicated with map section) will be better?