I recently updated the Digital Edition to 2.0. My wife and I share our home PC with each having our own log in. I can download and open books on my Kobo. But, my wife has a problem opening a downloaded book on her Nook. She gets an ERROR DIALOG on the Nook User not activated. We did not have this problem with the older Digital Edition. When I look at her Digital Edition "HELP", I cannot view the Digital ID but I can when I look at my Digital Edition. Does she have separately download a Digital Edition? It worked before?
ADE 2.0 has problems with some ereaders (and with lots of other things).
I suggest you revert to the older and more reliable previous version.
There are lots of bugs in ADE2.0. Try replacing ADE2.0 with the older but more reliable v1.7.2.
(You can have them both installed at once if you like.)
Version 1.7.2, it is a little difficult to find, available on Adobe site for Windows and for Mac.
The forum software is sometimes corrupting the link above. There shouldn't be a blank in 'editio ns.html'. The following redirects to the same page: http://tinyurl.com/diged172
Do you share an Adobe ID (that is the easiest way to go, especially as you share a computer)?