DRM Authorization

I downloaded books in my Kobo Aura H20 from a public library.  When I try to open it, it says that this reader is not authorized to open the book, which it's false since the authorization rights have been given to my pc and to my reader.  Some other people have the same problems and there is no solution proposed by ADE.  I desinstalled ADE 4.5 et reinstalled 3.0, but no success.  What is going on?