Digital Editions Library books to Kobo Glo

hello, 

I have an older Kobo glo and cannot download a library book on there. 

i have unauthorized and reauthorized a hundred times both the computer and the kobo. i have redownload the books multiple times as well. i have tried not opening it in ADE first. i have tried it all!!

I cannot figure it out. the book is in my kobo library but i cannot open it. it says i am not authorized.