nomatter what I do, I get "Please, enter correct Facebook API settings"

Hi,

I've been trying to utilize the Ultimate Facebook plugin; I have successfully created a Facebook App, added a website platform, inserted the url, and added the app ID and Key in the plugin settings page; but, I still get an error that reads "Please, enter correct Facebook API settings." I have tried with three different facebook applications and can't quite figure out what I'm doing wrong. I have followed all of the instructions on your site multiple times.

Any help would be greatly appreciated,
Christian