There are list of Troubleshooting Articles which may be worth Reading for Troubleshooting the Issues related to Symantec Endpoint Protection version 12.1:
http://techcenter.symantec.com/ecampus/enterprise?siteName=sena&courseNo=SAV6000
1) Troubleshooting Symantec Endpoint Protection
2) Symantec Endpoint Protection Manager 12.1 Communication Troubleshooting
3) Troubleshooting communication problems between the management server and the client
4) Troubleshooting communication problems between the management server and the console or the database
5) Recovering client communication settings by using the SylinkDrop tool
6) Troubleshooting reporting issues
7) Troubleshooting issues with Shared Insight Cache
8) Troubleshooting context-sensitive help for the reporting console
9) Symantec Endpoint Protection: LiveUpdate Troubleshooting Flowchart
10) How to clear out definitions for a Symantec Endpoint Protection 12.1 client manually
11) About commands you can run on client computers
12) Downloading the Symantec Endpoint Protection Support Tool to troubleshoot computer issues
13) Investigating protection problems using the troubleshooting file on the client
14) SEPM: poor database performance
15) Performing disaster recovery
16) Maintaining the database
http://www.symantec.com/business/support/index?page=content&id=TECH163580