I have the same problem, but in my case I've already have an authorization only the program won't accept it for some books.
This is what is says exactly (i translate):
"Impossible to download. Error in retrieving license. Problem of communication of server's licenses:
I cancelled the authorization and then i did it again and for one book, even if the same message error appeared, it worked, and now I can read it! So I tried with other book but... nothing! Same error, nothing works.