This is most common for people that are new to using library ebooks. The Nook did not automatically see the Adobe ebook security being used on the Cloud Library, so we are going to introduce it to Adobe security using Adobe Digital Editions.
Before doing this, close Cloud Library on your computer (to keep it out of the way) AND delete the copy of the ebook(s) from your Nook. You can transfer a fresh copy after the fix.
1. Go to the Adobe Digital Editions download page. Download & install the proper version for your computer (Windows or Mac).
2. When ADE is installed, open it. The software will see that you are already using Adobe security on Cloud Library and match it.
3. Plug your Nook into the computer. ADE will recognize it and show the name of your Nook under "Devices" on the left side.
4. ADE may have automatically updated Adobe security on the Nook when it recognized the device, but check by:
-Click the name of your Nook (under Devices) once to select it.
-Click the gear icon for the Devices area.
-This shows a menu. Select "Authorize device." If you cannot click this, then ADE did automatically update the device. If you can click it, doing so finishes the setup.
You may now close Adobe Digital Editions, reopen Cloud Library, and transfer a new copy of the book to your Nook.