[2020] Reinstalled on new PC, can't join friends because my instance is untrusted by Anti-Cheat

Only thing that comes to mind is that it’s possible you or your friends are playing on the Modded realm.

When you open the launcher, make sure your launcher says you are on the “Official Realm”, instead of the “Modded Realm”.

All players need to be on the same realm to play together.

I have responded to your submission via the Support Portal, with basically everything Kaelus has mentioned above. My reply may be in your ‘Spam’ inbox.