Not sure if this is a bug or if I'm missing something but on a new installation of docmenta 1.5.0, with no products yet, I have added a few users and made them belong to the Administrators group.
However, for none of the users the 'administration' tab is visible. It's only there for the 'admin' account.
i had the Same Problem. I found out that if the users have become a other group first then the admin tab is not there. so i first assigned them to admin then the other groups