This is not a problem, but something I fixed on my own that I'm placing in the forum for easy search and fix. Well, for at least newbies like me!
I was able to register users with the Ultimate Facebook plugin, but when I went to click log in with Facebook, it didn't take me anywhere.
I realized the redirect wasn't working correctly.
Under Facebook Connect in Facebook> Facebook Settings, I had my Redirect set at Site URL. Then, underneath, by default, it's blank. My redirect didn't work, so I placed forward slash and voila, the redirect works! Now I'm logged in!
This is something so simple to overlook! But now it all works!
Here's a pic!