Ultimate facebook is not working

Hi there,
I have installed ultimate facebook plugin. You guys have done great job. But I have faced a problem.
I see Ultimate Facebook problem registers user using wordpress default signup page: wp-signup.php
But in my site, wp-signup.php is disabled. We use our custom registration page: http://legiontraining.staging.wpengine.com/registration/

So, whenever I try to register with facebook, it says: registration is disabled. So what's the solution?

You can check it by yourself by browsing to: http://legiontraining.staging.wpengine.com/registration/