Recently purchased Mac (previously Windows-based - not sure if this is relevant though!). Installed ADE, and borrowed library book. Was able to download book onto computer, into ADE, and transfer to Kobo. However, when attempting to open on Kobo, it gave an error that I did not have rights to open the book, and that I needed to authorize (I think... didn't think it write it down).
After searching online, I tried erasing authorization of both Kobo and computer, and re-authorizing both. I then couldn't even download a book to ADE. I was told to delete everything, and try starting over. I am now able to download the library book on my computer to ADE, and copy it to my Kobo.
However when I try to open it on my Kobo, I receive the error:
"Your ereader is not authorized to open this book. This book is protected by Adobe Digital Rights Management (DRM). Because you previously deauthorized your ereader, you need to re-import the book using ADE". I have done this multiple times, and still can't open the book.