Problems connecting to shared folders

With my iPad or with another Mac I can connect to my Mac Mini (Late 2012, Mojave) shared folders using my Admin credentials without any problem, however when I try to connect with my wife’s standard account credentials, it always says that "access to your account on the server xxxxx has been denied".

The credentials are very much correct so that isn’t the problem.

I also have a MBP (2015, Mojave) set-up in an identical way to the Mini, and I can connect without problems to both accounts on that machine so the problem manifests itself only when trying to access the Mini.

Any suggestion?