I'm having a bit of trouble with the Facebook Login extension. It works fine if I use it to link a Facebook account whose email already matches an existing Flarum account, but if try it with a Facebook account whose email isn't yet registered on my Flarum, then clicking this "Sign Up" button simply does nothing:

I have debug mode enabled in my config.php file, but get no error message when trying to register. I noticed this problem after I received an email from Facebook saying "During Login, your app or website is crashing or hanging excessively".
Please let me know if there's any additional information I can provide to help debug. Thanks!