that was all I could think of.
i am not familiar with the 2 specific e-readers you have. Do they have matching PC apps for initial set up which may have to be run once on a new machine ( or a fresh install )
you have already tested your readers with a different PC, all that leaves is borrowing a kindle or a kobo and testing your PC with that, to try to narrow down the issue
PS a fresh install will have wiped any adobe ID registration from the PC . it is a long shot but installing the version of ADE you used before and going though adobe registration may cause the reader(s) to be recognized
one more long shot . This "fix" was for a Kobo but who knows. - its worth a try...
https://answers.microsoft.com/en-us/...9-1b909e856bf5
"We just stumbled upon a solution - we turned off the wifi on our kobo glo, and then suddenly the kobo asks that familiar question - "do you want to connect?" Tap yes, and it's back to normal.
We load books from local library via Adobe Digital Editions - and we normally get prompted by the kobo glo to connect when the usb cable is plugged in. We lost that message until we turned off the wifi on the kobo