Make sure you are using the same AdobeID on ADE1.7.2 and on the device;
and that that is the ID your books already know about.
To clean things up I suggest you start registration again.
- Plug in device to usb.
- Clear device authorization (ctrl-shift-E and respond to prompts)
- Clear ADE authorization (ctrl-shift-D and respond to prompts)
- restart ADE
- Authorize computer with your AdobeID (not as 'no ID' if that is offered).
It may ask automatically, or you may need menu/Library/Authorize Computer, and enter your Adobe username and password. - Authorize device
It may ask automatically, or you may need menu/Library/Authorize Device