I cannot connect to the game if there are more than 6 people in it. If I join one of the first ones, everything is fine. This problem appeared about 3 months ago, but then disappeared and now it has reappeared.advanced-ice-adapter.log
connect trabl
AFAIK One of the next major steps for the developers is to narrow down the issue on the ongoing connection issues which some people encounter lately. The developers have just finished improving the Login Service recently https://forum.faforever.com/topic/6429/login-service-update/1
It is extremely hard and time consuming to debug the network stuff so the "ultimate" solution will take some time.
If the issue is not related to your security settings like firewall or router, then unfortunately I have no idea how you can solve it on your side - except to try it on a fresh Windows with a default environment.