I keep getting this message and older forum discussions (2012-13) have not helped me, so putting this out there again in case there is another answer. I downloaded the ADE 2.0 and when I tried to download a library ebook, I got the authorization window. I've done this many times before because I do this for the library where I work. But the error message kept popping up.
I've tried cancelling and retrying, no luck. I've tried the cntrl+shift+D but nothing happens when I hit those keys. The computer runs Windows 8. Could that be the problem? In a previous forum, someone said he tried it over a few weeks before it worked. Obviously this is difficult to do when working with someone else's computer.
You need to be in Library view when you hit ctrl-shift-D.
I've not heard of other reasons for it not to work.
I can confirm it does (or at least can) work on Win 8/8.1; at least as far as bringing up the confirmation dialog, and you are saying it didn't even get that far.
It won't need to talk to any Adobe servers till later in the process so retrying is unlikely to work.
Maybe it has broung up the dialog and hidden it somewhere silly?
If the dialog is up, you should see a double icon for ADE in the Windows taskbar.
As an extreme if it really doesn't work, backup the registry, go to the registry editor,
and delete key HKEY_CURRENT_USER\Software\Adobe\Adept\Activation and everything below it.