For my users in Active Directory, I did setup a GPO in order to allow the remote desktop connections.
For a specific user in particular, I did also manually setup the group membership for Remote Desktop Users:
However, I still get an error while performing a remote logon, saying that the user is not allowed to login in remotely.
Do you have any clue about it? Please just consider that Admins can correctly perform this operation, and the target machine is a generic windows server machine (no specific role yet installed, just joined to the domain).