Nook hooked to the USB, why library books not showing up on ADE?

I have three e-books from library on my nook, but none of them will open; they were fine this morning. Nook is charged to 79%.  When I plug in USB, my Adobe Digital Editions shows books on my bookcase, but the Nook does not show up.  I've been doing this for several months, so I do know how to use it. Just in case, I tried using a USB cord from my phone (same size plugs), and ADE still not showing my Nook ebooks. I can open books I "purchased" or got for free that were put directly onto the Nook, but not any books I've borrowed from a library.  Can anyone tell me what's wrong?  I'm assuming the USBs work okay, since the little nook light next to the plug is on.

I spend several hours a day reading my nook.  Whatever will I do now!   Yikes!

Thanks all!