It is not a problem regarding certificates. Those are only symptoms.
In the server log you can see every endpoint that was requested.
modules.log also shows every url that is requested.
Client's log show this error:
Code
|0.12.11.2.14290|Error|backend|<--- Error! URL: https://127.0.0.1/client/game/start, isNetworkError:True, isHttpError:False, responseCode:0, error text: Certificate validation error
But this URL is nowhere to be found in server.log or modules.log.
It looks like the "patch" did not apply (or was removed by the game). But my coding experience is too small to keep diging further. Can any one tell something more about this issue?
EDIT:
I have Windows 10 original with latest patches. Maybe this is an issue?