Register with Facebook not working

The Register With Facebook button is not working on my membership sign up page. When you click the icon, the page reloads, but facebook registration is not enabled. I am enclosing a screen shot in case it yields some clues. I don't know what this should look like but I thought the "login with facebook" below the basic registration fields looked a little naked, so perhaps there is some info there?

Once a user is registered the "login with facebook" works perfectly - thought oddly the icon is a little wonky - enclosing a screenshot of that as well, again in case it yields clues.