I can't copy a rent e-book on a reader

Hi I have Adobe Digital 2,0 on mac and it's works good but when i rent an e-book from the "bibliotheque national", I can read them on my computer but when I drag them on my reader (kobo aura) it said "COPY-NOT-ALLOWED" I put the same user name on my computer and my reader so it's supposed to work. I also allow my computer and my reader. Can anyone know what to do?