A while ago I bought an e-reader that could no be authorize, so the shop changed it and I could authorize it. Unfortunately the reader had other problems and I gave it back to get another one... unfortunately with the same problem. Finally I bought a new one somewhere else. That means the there are 2 readers good for nothing that account for the 6 devices I can authorize.
If one day I need to authorize another computer or reader... where do I have to ask for that????
I looked around but could not find the right place.