I haven't seen this problem mentioned by anyone else (but I may have missed it) so I started a new thread.
My Kobo updated the other day to 2.4.0 and now all my ADE DRM protected epubs will not open. I get a message that says
"This document is not currently authorized for use with your Adobe ID. Please sign in and try again"
The settings info on the Kobo says that I am signed in with the correct Adobe ID and the Kobo is recognised when I open up ADE on the desktop. I can read the ebooks on the ADE desktop and on my Sony PRS-650, it's just the Kobo that refuses access.
Any ideas please? Also, I'm just a reader, I get sort of lost when I see answers to others that involve things like rewriting code and changing files or whatever
ETA: this is only happening with epubs that were not bought from Kobo - the ebooks from the Kobo shop are ok but none of the others.