I can download books from my library and read them on ADE AND transfer them to my kobo, but on my kobo appears a black thumbnail instead of the book cover and when I open it a pop up appears that says, "Oops! This document couldn't be opened. This document is protected by Adobe Digital Rights Management (DRM) and is not currently authorized for use with your Adobe ID. Please sign -in with the authorized Adobe ID and try again."
I have done a lot of things to fix this problem ... deauthorizing the device and ADE. I have reinstalled ADE, I even have a new computer that I installed ADE on and it is still occurring.