Does the Nook show up on your file manager (Windows Explorer, Mac Finder) as a mounted drive?
If not, the problem is before you even get near to ADE. Check the Nook hardware and your USB connection.
If so, first se http://help.overdrive.com/article/0047/What-to-do-if-your-NOOK-is-not- detected-by-Adobe-Digital-Editions
then try v1.7.2 as above.