I've replaced my Kobo Touch with a Sony prs 650 -Adobe Digital Editions won't sync

I've replaced my Kobo Touch with a Sony prs 650, and I can't get Adobe Digital Editions to recognise it.

Initially the Prs650 appeared in Adobe, but after downloading some ePub books from my Public Library, the PRS 650 disappeared form Adobe, and I can't find any way to get it to appear again.

The PRS650 Downloaded the Sony EReader Library, but this wouldn't function and referred me to the KOBO Libray, where I already have an account.

Any clues?

Thanks!

richjenn13