Hi,
Thank you for posting in Symantec community.
If only Virus & Spyware definitions are not updating then I would recommend to run JDB file to update definitions file manually.
Refer the following article:
How to update definitions for Symantec Endpoint Protection Manager (SEPM) using a .jdb file
http://www.symantec.com/docs/TECH102607
Have you tried to repair the SEPM?