check this
Clients cannot send data back to Symantec Endpoint Protection Manager
http://www.symantec.com/docs/TECH105348
Kindly try this troubleshooting step:
1. Browse to \Program Files\Symantec\Symantec Endpoint Protection Manager\data\outbox\agentinfo
2. Look for any .err files or tmp files & Dat files
3. If you find anything which is not processed by sepm then it might be the reason for the client data loss
4. Stop SEPM services from services.msc
5. Delete all the files inside the location \Program Files\Symantec\Symantec Endpoint Protection Manager\data\inbox\agentinfo
6. Restart the SEPM services.
Check the SEPM now if still issue persist go for step 7
7. Run the Management server configuration wizard.
Note: While running Management server configuration wizard it requires Database password. if you running SEP 12.1.2 it wont prompt you for DB password.
Kindly update us the status .... thanks