After upgrading to Windows 10 on my desktop computer, I suddenly could not download books to ADE, and got the above error message. I tried upgrading my ADE 2 to ADE 3 and then ADE 4. I uninstalled the older versions, and then reinstalled them. I removed all my books from my "My Digital Editions" out of the default library, and then tried to open them in the new ADE. Now I can't even look at these on ADE. I also cannot move books from my Nook onto my ADE on the computer. At one time I also got the E_ADEPT_REQUEST_EXPIRED error. I stopped getting that when I uninstalled ADE 4, rebooted my computer and then reinstalled ADE 4 all over again, after moving my files. Nothing is working - not fixing the time on my computer and not running ADE as administrator. The funny thing is, on two laptops (one running Windows 8 and the other running Windows 10) ADE 4 works fine.
Please try with the latest version of ADE 4.5.2 - Download | Adobe Digital Editions and check incase it works.
The error message seem to pointinf to some old corrupt information.
Can you please confirm when exactly do you see this error (while launching ADE, opening/moving specific books or with all ebook)?
Please try downloading an ebook from the sample ebook library- Sample eBook Library | Adobe Digital Editions and check if you see any error.
It would be helpful if you could share a screenshot of the error message as well.