In my opinion, most of the error messages are related to authorization (but I'm no expert!). The reader's software knows if you really have purchased the license for the book or not. If you have a license to read the book, then try deleting all authorizations - from the computer, and from the ereader. Then try downloading the book, clicking it, and adobe will prompt you for the exact authorization. Enter where you got the license from the drag-down menu, then your email and password for that place and you should be able to then open the book and drag it onto the reader.