Digital Editions stuck at fulfilling

I had a similar problem, where ADE 4.5.9 wasn't working for me. I tried everything I could think of. I tried reinstalling, I tried rolling back to 3.0, I deleted the Adept key and tried logging on again, etc. What finally worked for me was to purge my computer of everything Adobe and starting over.

I first uninstalled everything with Adobe in the name (including flash player and Adobe Acrobat DC). Then I went to REGEDIT, and under HKEY_CURRENT_USER, software, I exported the entire Adobe key (just in case I messed it up), and deleted it. I then went to my C:/Program Files (x86) folder and deleted the adobe folder there. I then went to my Documents folder and renamed the "My Digital Editions" folder so Adobe Digital Editions wouldn't point there.

Finally, I re-installed, re-authorized the new program, and the next book I tried to open worked. Whether that's a permanent fix, or something I'll have to do again, I don't know... but it works for now.

I have the same problem. And the book is checked out according to my library account, but I cannot return it from ADE because it never actually finished fulfillment.

Also, another subject:  what's with all these deleted/returned books showing up again in ADE all of a sudden?

I run Windows 10 on a PC and just installed ADE 4.5.4 today, after uninstalling ADE 3.0.

Sorry, this is not really an answer to the first post, just another person with a similar issue.