Kobo Aura account says not authorised withAdobe Digital Editions

I have a kobo aura. I used it exclusively to borrow book from the library through Borrowbox: I go onto the library site, dowload the books I want to read, the downloaded files are transferred automatically onto the Abode Digital Editions on my laptop. I hook up the Kobo which appears on the ADE windows and I drag the file onto it.  I have done this too many times to count.

Today my Kobo wouldn't appear on the window.  I eventually figured out that under my account on the Kobo, it says "Not authorised with Adobe Digital Editions".

What?? How??? And how can I rectify this? I contacted kobo but they weren't helpful.