Hello,
Could you please let us know - which setup are you trying to run on the SEPM server??
Secondly, check these articles:
SEPM 12.1 RU1 Small Business Edition won't upgrade to 12.1.1 MP1 saying you are not allowed to downgrade from Enterprise Edition.
http://www.symantec.com/docs/TECH189041
How to disable Tamper Protection in Symantec Endpoint Protection 12.1 Small Business Edition
http://www.symantec.com/docs/HOWTO77121
Best practices for upgrading to Symantec Endpoint Protection 12.1.x
http://www.symantec.com/business/support/index?page=content&id=TECH163700
Hope that helps!!