Re authorise your ereader

I read a lot of books on my Kobo.  If I purchase books from Kobo I do not have a problem.  But EVERY time I borrow a book from the library and I download it to Digital Editions I get this message:

Your e reader is not authorised to open this book.

This book is protected by Adobe Digital Rights Management. You need to reauthorise your ereader with your Adobe ID using Adobe Digital Editions.

When I do this, it still does not always work and the same message appears.  I can do it several times and then it is only by luck that it works.  
If I do reauthorise for a new book, then I have to download all the other books that I have previously borrowed.  
This is hopeless.  It should not be occurring every time I try to borrow a book.  It takes hours to try and fix and it doesn't always work.  Really bad software.