Login failed for user 'NT AUTHORITY\SYSTEM' I tried to add NT AUTHORITY/SYSTEM to SSMS (SQL Server Management Studio) logins, but it was already a principal, showing the following error: Solution : https://stackoverflow.com/questions/24822076/sql-server-login-error-login-failed-for-user-nt-authority-system Allow NT AUTHORITY/SYSTEM to server Role as sysadmin.