I cannot access my book borrowed from a library, on my Kobo anymore. The message: "This book is protected by DRM. Reconnect with your Adobe authorized ID."

I cannot access on my Kobo a book borrowed from a public library anymore. This is the first time I borrow a book from a library. I think this comes from the 21-day borrowing period allowance. The message is: "This book is protected by Adobe Digital Right Management and can not be open with your Adobe ID. Connect with your authorized Adobe ID and try again. www.kobo.com/help." I did that, but nothing significant happens. I do not know how to keep going. I do have a MAC.