Login failed for user Error: 18456, Severity: 14, State: 11 I have an AD group XYZ that I have added to SQL Server security with data_reader permissions.

The XYZ group has around 10 users in there who are successfully able to access the SQL Server database. I recently added a new user to this group (at AD level), but this person is not able to access SQL Server (through Mgmt Studio) and he's getting the error below


  Login failed for user. Reason: Token-based server access validation failed with an infrastructure error. Check for previous errors.
  
  Error: 18456, Severity: 14, State: 11.


I have already verified AD permissions are setup properly, user has restarted his machine, he is not part of any group that has DENY access and  the SQL Server XYZ group has been removed and readded to the SQL Server instance in Mgmt Studio and server has been restarted. 

Any ideas on how to proceed further?

Thanks!
States 11 &amp; 12 mean that SQL Server was able to authenticate you, but weren't able to validate with the underlying Windows permissions. It could be that the Windows login has no profile or that permissions could not be checked due to UAC. Try running SSMS as administrator and/or disabling UAC. Another reason could be that the domain controller could not be reached. 

Refer to to the below link for more information on Error states.


https://sqlblog.org/2011/01/14/troubleshooting-error-18456