See error message below:
Can't Load URL: The domain of this URL isn't included in the app's domains. To be able to load this URL, add all domains and subdomains of your app to the App Domains field in your app settings.
The www variant should not be listed in the App Domain. Only the first value that you have in there should be.
* Could you go into the JFBConnect backend > Autotune > Facebook App tab? Look through the settings and see if there are any values in there that are marked red (specifically in the Application and Website Links sections), then make any appropriate changes and try logging in again.
* What is the specific URL of the page you're performing the login action on?
* Can you provide a URL where I can see the Facebook login buttons on the front-end? Visiting your page, I do not see the SCLogin or the social buttons when I go to the Joomla Users component login page (index.php?option=com_users&task=login). If you want to add the buttons really quick to the com_users page, you can add them with the Integrate into Joomla Login setting.
* If these above points don't help us narrow down the problem, I would also suggest also reviewing our Facebook Application Setup Guide to make sure you're following the correct setup of the application.
I was able to create an account successfully on your site with my Facebook credentials with no error message. However, It looks like you've disabled auto-login so I can't see the error behavior in action. Could you re-enable it so I can check out the network activity/URLs in the browser dev tools?