The Defender Security Server (DSS) object in Active Directory (AD) has a red light on the "Security Server" tab of the object's properties.
Verify that the IP address entered on the "Security Server" tab is correct and corresponds with the actual IP address of the server where the Defender Security Server service is running.
The DSS object must be in the "Security Servers" OU. If it is moved the status (light) will remain red.
Verify that the DSS service is running and can authenticate successfully with AD.