After successfully using my kobo reader for library books for the last year, now when I try to transfer a book from my ADE4.5 to my kobo, I am getting a message which says "oops! this document couldn't be opened. This document is protected by DRM blah blah blah. I have unauthorised and then reauthorized my computer, and can read the books on my screen, but even though it looks like I have moved the books to my kobo reader, when I go to the home page I can't open them. I am a LOL and not very computer literate, so please make any suggestions super easy.