I have an Adobe ID & Password, but still can't authorise my computer?

Why has this question from April not been answered?! I just bought an iPad Mini and can't authorise my Adobe ID. I am trying to download books from my local public library through OverDrive, which I have been doing for years on my PC and my iPad but it's not working on my brand new Mini. When I click on a book that I've 'checked out' in my Bookshelf (in the 'library') it opens up the Adobe Authorisation window, which says, 'To use this eBook you must first authorize this application with an Adobe ID.' I enter my email address and password, click on Authorize. Then I get a pop up message that says: 'Adobe ID. This Adobe ID is synced to OverDrive. Would you like to log in to OverDrive and restore this activation? No/Yes.' When I click on Yes it takes me to an OverDrive window, asking me to 'Sign in to your OverDrive account'. I log in via Facebook, it opens up the Personal details page of Account Settings. I click Save, then it says 'Your account settings have been updated.' Then nothing else happens. When I go back into my OverDrive Bookshelf I have to do the whole process over again. Obviously the Adobe ID is not authorising somewhere along the line.