facebook 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. code example

Example: The domain of this URL isn't included in the app's domains. To be able to load this URL, add all domains and sub-domains of your app to the App Domains field in your app settings.

This usually happens if you have entered the wrong details when you created
the App in Facebook. Or have you changed a URL's of an existing App?

Can you please recheck the settings of your APP in this page?
	https://developers.facebook.com/apps

1. check submitted oauth redirect uri. and also test it below to check if its 
valid or not
2. Select the correct App and click in the edit button;
3. check the URLs & paths are correctly entered and are pointing to the site
where you have installed Ultimate Facebook plugin.