You had SEP 11.0 Enterprise edition or Small business Edition?
Are you trying to use the Enterprise edition license with SME 12.1?
Register your license first and then use it , follow this document
How to upgrade your Symantec Endpoint Protection 11 license to Symantec Endpoint Protection 12.1 online
http://www.symantec.com/business/support/index?page=content&id=HOWTO56030