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. Facebook Login

I had same issue (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) by updating SDK version solved the problem 

Solution: Simply update your SDK to latest version to 5.6.2 or 5.6.3 will solve the problem.