Could not obtain information about Windows NT group user
Active Directory is refusing access to your SQL Agent. The Agent should be running under an account that is recognized by STAR domain controller.
Could not obtain information about windows nt group/user sql server error
This might help someone in the future. This error can occur which did for me because I was logged in as Domain User and was not connected to local User. This error can be fixed by changing the database owner to [sa] account.
Could not obtain information about Windows NT group / user, error code 0x3a
This issue wasted so much time I feel compelled to share the solution so that nobody else falls into the same trap.
Issue was resolved by setting the SQL Server Active Directory Helper service to run on Manual, then rebooting the server.