Downloading Books to Adobe Digital Editions

I recently got a new computer and have been trying to download an ebook that I borrowed from the local library onto my ADE. I tried using the Epub format since that is what I used on my ADE on my past computer, but it has not been working. I tried another book with an open Epub, and that worked fine, but the book I'm trying to get does not have that option. I'm just trying to figure out why normal Epub isn't working anymore and trying to see if there's a way to make it work.