reset authorisation ?

I’m having a problem downloading a book I ordered from a bookshop. During the process of downloading the book via ADE I must have authorized my new computer without my ADE-id but I don’t want to read the book on the computer but on my Kobo e-reader. So I removed everything from my computer and downloaded again the file from the bookshop. This time I correctly authorized my new computer with my ADE-id but when I want to download the book I get the message hereabove.