can't authorize my computer

im trying to authorize my computer for it to be able to use my digital editions, i need this because i downloaded a book without doing it first and because of that i can get the book to work on my other divices because the licensing only allows me to download it once. when i try to authorize my computer i get a message that says (you can only authorize this device with an adobe ID that hasnt been previously used to authorize any other equipment or mobile device) or something along that line (i translated it from spanish). im only logged in in 2 other devices with my adobe ID, I read you can be on 6 devices at the same time.