Hey there Comeforu,
I’ve been seeing a few reports where players who have an authenticator on their account already are not able to make a custom description for the group. It’s being looked into by the developers. The notes I found mention that having SMS set up for the account can help though. Please see if setting that up helps. This page gives a bit more information and also acts as a good starting point to get that done. If there is still a problem, then please report it as a bug so the devs can get some more information to more directly address what’s going on.