This is very simple but so many might get this error very often, especially when you created a maintenance plan and run it we may get below error:
The job failed. Unable to determine if the owner (XXX) of job DATABASE Maintenance.xx has server access (reason: Could not obtain information about Windows NT group/user ‘xxx, error code 0x534. [SQLSTATE 42000] (Error 15404)).
so we should always change the owner of the job to “Sa” once we create a maintenances plan and scheduled it. because we may not have access to run the job or if we are admin on the box and sql server and we are good initially, but when we left the organization and our account is disabled from windows AD group, we may get this error.