SEP upgrade from 12.1 MP7 to 14 not working

Hello,

After stopping the Symantec Endpoint Protection Manager service, I tried to run the installer for SEP 14. It automatically knew to upgrade, but then gave me this message:

"Upgrading from your installed version of Symantec Endpoint Protection Manager is not supported. Installation cannot proceed."

MP7 should be supported. What's going on?

Thanks,

-Alex