Double-check times and time zones on the PC where you did the original download, and on the nook.
Even if they were wrong and you correct them, it may be too late for a book it has already decided is past its borrow-by date,
so check on another book.
I don't think that is the case because I downloaded the same book onto my nook color and am reading it now. I don't understand what happened with the nook hd. I will however try it with another book. - thank you
but the timezones on the PC and the nook colour could agree; with the timezone on the nook hd being out of sync.
I looked at the times zones - the pc is "(UTC 5:00) Eastern Time (US & Canada)"
The Nook Color is "GMT- 4:00 Estern Daylight Time"
The Nook HD is the same as the Nook Color.
Do you consistently get the same with new books that you borrow, or is it just the one book giving problems?
I just tried another book and has the same problem. I was able to download and read a book that was in adope acrobat reader format. Re the ADE books I sideload as follows- I view the list of books in ADE in explorer and copy the epub books from there to my Nook HD.
What app are you using on the Nook to try to read the epub?
Try installing Bluefire and/or Aldiko apps (both free), registering those with your AdobeID, and see how they manage.
Also, for library books you can install the OverDrive app; with that should be able to borrow, download and read library books on the tablet with no need for ADE or a PC/Mac at all.