When you restore database backups from one instance to another, the previous ""MAS_Reports"" SQL login permission comes along for the ride, but the ID for the login will not match between the two instances. This means that you need to remove the old permission, then re-add it, so the SQL login for the current instance has it's ID# used for the settings.
The same issue applies to database ownership, but since you didn't complain about not being able to work with the copied data, I omitted the part of the script that sets MAS_User as the db owner.