Hi,
Check this article, it sounds like the issue that you are experincing.
After installing Symantec Endpoint Protection 12.1 on a machine, you receive a warning that the trial license has expired even though the SEPM has an active non-trial license.
http://www.symantec.com/business/support/index?page=content&id=TECH171252&actp=search&viewlocale=en_US&searchid=1324503000884
I am moving this thread to the corrrect forum for you (Endpoint Protection).