Monitors that the Group Policy Client service is running on this domain controller. This service is responsible for applying settings configured by administrators for the computer and users through the Group Policy component.
If the service is stopped, the settings will not be applied and applications and components will not be manageable through Group Policy. And components or applications that depend on the Group Policy component might not be functional if the service is stopped.
Verify that the Group Policy Client service is set to automatic start and is running.
Check the Application and System event logs to ensure that there are no systemic problems with the server.