I just paid to upgrade to the current paid version and followed the instructions here: http://ellislab.com/expressionengine/user-guide/installation/upgrade_from_core.html
I added the license key to my config file before I added it back. But I am still being invited to upgrade from core. What am I missing? I replaced all of the files and directories as specified and cleared the cache. The license key is showing up on the Admin config page but the banner at the top is telling me I have core.