Forza Horizon 4 can't join online session (PC)?

Have had the problem for a few days that I can't join an online session. There's nothing or no errors under Network in the Xbox console companion app, so everything should work.

I can't join an in-game session, but downloading designs or tunings works just like the auto fair

Then Forza is going to zick again. I already had

No, that can't be been 3 weeks already…