Sometimes ADE gets its registration/activation confused and in a semi-authorized state.
Uninstalling and reinstalling does not help, and indeed installation can even trigger this state.
Unfortunately, it often then gives misleading error messages about what is wrong.
A common incorrect message informs you that the ID is already in use on another computer and cannot be reused.
Another is "E_AUTH_NOT_READY"
This can often be resolved by completely removing any authorization using ctrl-shift-D to the Library screen on ADE (cmd-shift-D if on Mac).
Restart ADE, and then reauthorize with your (old) Adobe ID.
In extreme cases on the mac, the following extra step has helped some people. Navigate to /Users//Library/Application Support/Adobe/Digital Editions and drag the activation.dat file to the trash. If you are using 10.7, see Access hidden user library files | Mac OS 10.7 Lion. http://forums.adobe.com/thread/1265248?tstart=0
Tried this, filled out form, hit send, all if get is a blank screen, waited for 1/2 hr.
Waited in the chat screen
Pretty hopless service. All I can suggest is to try a different time of day, or try telephone service
(not sure of the number, and they are even worse than online chat from what I have seen on the forum)
Or the Adobe Support Portal
https://www.adobe.com/cfusion/support/index.cfm?event=home&loc=en_gb for GB and maybe for UK
I'm sure you can easily find yours.
I've never used any of them so can't give personal opinion.
Good luck ...