It might help if you would say, what exactly you cannot do.
Because it is quite obvious, that you can access your account and open a message board thread. If Itch would ban you, they would ban your account.
If you cannot comment on games, see all the other threads about it. It's the spam filter and that thing is very aggressive.
If you cannot access game pages, is this game specific or can you not access any game page? Try some of the featured games here https://itch.io/
Same for downloading.
Itch installed some aggressive bot protection that will have your browser prove that you are a human. That can go wrong and it will not last all day. Even the Itch app did not work properly because of that.
