Could you check in the SEPM >Admin > Domains, see 2 domains listed?
"default" be the only 1 domain listed.
If there is only 1 domain listed, then try the steps provided in the Articles below:
1) Symantec Endpoint Protection Manager 12.1 Communication Troubleshooting
http://www.symantec.com/docs/TECH160964
2) Troubleshooting communication problems between the management server and the client
http://www.symantec.com/docs/HOWTO55017
Hope that helps!!