how to get Adobe Digital Editions to give me permission to transfer ebooks to my Kobo

I have recently purchased a MacBook Air and am trying to get Adobe Digital Editions to allow me to transfer ebooks to my Kobo.

I previously had ADE on my PC and it allowed transfer with no problem.

On the MAC, I am getting an error message that I do not have permission to copy the book, but it is also saying that my Kobo is 'authorized.'

The library told me to 'Erase Device Authorization', but in doing so, now I can't read anything on my Kobo.