I went to this link
https://adobe-digital-editions.software.informer.com/3.0/
Make sure you download the 3.0 program. Just be careful.
it downloaded to me just fine. I installed it.
Now go to the version of ADE that is currently installed on your computer and deactivate the authorization.
Go to the 3.0 version and activate the authorization IN THAT VERSION.
Add your Nook as another device if it didn't automatically. Remove the library books from the Nook Library and your ADE library. Go to your library and download the book/s again. Now transfer the book to your Nook. This should work. it did for me.
Good Luck
