title: Redirect URL not getting called when authenticating using Xamarin.Auth
body: <p>I am starting to build an app that authenticates to a third party web service, and I'm having problems getting the authentication working. The login page is displayed correctly, but once the user logs in an error message is displayed: "The URL can't be shown".</p>
  
  <p>I'm working on the iOS version of my app first, so I've only tested this on iOS so far using the Simulator. I initially thought that I wasn't registering the URL scheme for the redirect URL correctly, but if I put a breakpoint in <code>AppDelegate.OpenURL()</code>, and enter a URL with my URL scheme in Safari my app is launched.</p>
  
  <p>Handling the <code>OAuth2Authenticator.Error</code> event didn't give any more information beyond the same error message.</p>
  
  <p>This is my first time working with Xamarin Forms and Xamarin Auth, so I'm not sure what else to do in order to debug the problem. What else can I do in order to figure out the root cause of this error?</p>