In ADE, try clicking the "Help" tab up at the top left, then click "Authorize Computer."
I can't authorize the computer as it says it is already assocated with an adobe id. Still unclear what can do. We recently had to convert our Sony Library to Kobo so hence all the troubles. The old Sony library books are books are on the Kobo library. The ereader has been authorized as well as the computer. So not clear on what to do now.
I'm in a similar boat... I just had to transfer to Kobo from Sony as well, and I can't get my eReader to connect to ADE. Hopefully somebody else here will know what to do, although it doesn't seem that there are many people here :\
Have you tried doing a live chat with a Kobo representative? They didn't know how to help me, so I have to call, but maybe they can help you? The person I chatted with seemed to have a basic understanding of ADE.
http://www.kobo.com/help (Scroll down to the bottom, and click "Contact Customer Care" next to the blue "Ask" button. Then click Live Chat)