Recently, my Digital Editions stopped working completely, and would no longer open. I tried restarting my laptop, verifying files, all of that, and it still would not open. Upon uninstalling and reinstalling, every time I try and add a book to Digital Editions, I get an "Error! Check Activation" message. My computer and Digital Editions are registered, and I have absolutely no idea how to open books anymore. In desperate need to know how to fix this, as I use Digital Editions a lot for my work, and I am now seriously behind due to the application not working, and now even more behind due to this. Thanks.
Close all applications.
Press WINDOWS + R.
In the Open text box, type regedit and then press Enter. The Registry Editor opens.
In the left pane of the Registry Editor, locate the following registry key: HKEY_CURRENT_USER\Software\Adobe\Adept
Remove the Adept Folder.
In the Confirm Key Delete dialog, click OK.
Close the Registry Editor.
Open Adobe Digital Editions and reauthorize..
quit Adobe Digital Editions.
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 https://helpx.adobe.com/x-productkb/global/access-hidden-user-library-files.html
Open Adobe Digital Editions and reauthorize.