After restoring a database from a remote server backup, the “Login name” is often disassociated.
USE [database_name]; GO EXEC sp_change_users_login 'Auto_Fix', 'Username'; GO
SQL should respond with the following:
The row for user 'Username' will be fixed by updating its login link to a login already in existence. The number of orphaned users fixed by updating users was 1. The number of orphaned users fixed by adding new logins and then updating users was 0.
For more info: