Hi Martin, I suggest look for differences between this user and other users.
(like language on the user, special characters in the user code, when and how it was created, this users's access group and access related options).

Not seeing modules in the interface usually refers to incomplete language hobs.
If this user doesn't see modules, but other users do, my guess is that this user is looking for hobs in a different language.
I'd try adding the language of the other users to the broken user's Person and Global User cards specifically.

Difficult to say what is wrong 100% exactly, but I suggest to make those tests, hoping to find what causes the issue.