Solution: Deauthorize and reauthorize Adobe Digital Editions.
For Adobe Digital Editions (Windows PC and Mac)
De-authorize Adobe Digital Editions (from library view, CTRL+SHIFT+D or CMD+SHIFT+D).
If you have previously downloaded your book to another computer, please use the same Adobe ID when authorizing subsequent devices.
For Bluefire Reader (iOS and Android mobile devices) Click "Info" at bottom right of Bluefire Reader.
Click "Deauthorize" and confirm.
Click "Authorize" and enter your Adobe ID credentials.
After following the above steps, please try downloading and opening your book again.
Verify that your computer has access to the internet. If it does, check any proxy, firewall, or antivirus settings that may be preventing Adobe Digital Editions from accessing the internet.