Hi,
Thank you for posting your query on Symantec community.
Mentioned issue we have seen commonly in many cases, it could be due many reasons. Most common are as per below
1) Ensure that all Symantec services are started
2) Verify communication to the embedded (Sybase) database OR SQL database.
3) Check Hard drive space
If the still issue persists, perform the Repair on the Symantec Endpoint Protection Manager from Control Panel>>Add/Remove Program..
If the above steps did not resolve the issue, examine the scm-server-0.log & catalina.out file for possible indications of the cause. By default, this log is located in C:\Program Files\Symantec\Symantec Endpoint Protection Manager\tomcat\logs.