AutoUpgrade is not supported for an upgrade from version 12.1.6 or earlier. For example, you cannot upgrade from 12.1.5 to 14 using AutoUpgrade.
http://www.symantec.com/docs/HOWTO125379
Since AutoUpgrade was first included in the Mac client with Symantec Endpoint Protection 14, you cannot upgrade with AutoUpgrade from a version earlier than 14.