I downloaded the Adobe Digital Edition when I try to download my resource books I get this Error "Error: check activation" what could be wrong?

I had to erase my computer authorization, then re-authorize.

Afterwards, I could add the new purchase to the library.

Have you activated Digital Editions with an Adobe ID (or a Vendor ID)?

Go to the Help menu and select Authorization Information...

A window will appear to display your authorization information. If your computer is not authorized, you'll need to do that before you can read any DRM-protected books. If you don't have an Adobe ID, you can create one here.