Checking "allow ICE adapter to use IP6" and "force relay connection" solved it for me.
However, I do have some lag issues now.

It could be that I have the same problem.
I used to be able to join ladder games without any issues but since yesterday's update I can't join ladder games anymore.

It seems to be that I'm stuck on "Match launching" but the FAF client doesn't start Supreme Commander: Forged Alliance (see first screenshot with task manager).
After about 30s, it looks like I'm out of the queue and if I want to rejoin, it says that I'm in the state "STARTING_AUTOMATCH" (see second screenshot).
After another 30s or so, it gives another message that I'm causing connection issues and that further cases will give me a penalty.

I've already tried:

• creating single player games -> no issues, game start as normal
• clearing cache -> doesn't resolve the problem
• reinstalling FAF client -> doesn't resolve the problem

As there's no error or crash message, I don't get a log or something that I can give you to help find the cause of the issue.
So I don't really know what to do.