Moved to new PC. Digital Editions will not accept my Adobe ID to synchronize with my ebook (letto)

I realize this is a common problem, but I did not see any solution in the forum.

I have a letto e-book reader and I borrow books from library, all has worked well for several years, but when I now switched PC, it will not allow ebooks to be transferred to Letto - and it will not authorize my device as it is already authorized with my old PC (no longer existing),

There should be some easy way to resolve this, as this should happen eventually to everyone.