PlatformEffect fails to attach?

I believe I am having trouble getting a PlatformEffect to attach. It appears that it is resolving but not attaching. Here is the PlatformEffect in an iOS library project named EffectTestLib.iOS:

using System;
using Xamarin.Forms;
using Xamarin.Forms.Platform.iOS;

[assembly: ResolutionGroupName ("MyCompany")]
[assembly: ExportEffect (typeof (EffectTestLib.iOS.MyEffect), "MyEffect")]
namespace EffectTestLib.iOS {

    public class MyEffect : PlatformEffect {

        protected override void OnAttached () {
            System.Diagnostics.Debug.WriteLine ("Effect Attached");
            throw new NotImplementedException ();
        }

        protected override void OnDetached () {
            throw new NotImplementedException ();
        }

        protected override void OnElementPropertyChanged (System.ComponentModel.PropertyChangedEventArgs args) {
            base.OnElementPropertyChanged (args);
        }
    }
}

So, if it attaches, it SHOULD output "Effect Attached" and throw a NotImplementedException.

Here is the PCL code for the application that uses this PlatformEffect:

using Xamarin.Forms;

namespace EffectTest { 
    public class App : Application {
        public App () {
            MainPage = new ContentPage {
                Content = new StackLayout {
                    VerticalOptions = LayoutOptions.Center,
                    Children = {
                        new Label {
                            XAlign = TextAlignment.Center,
                            Text = "Welcome to Xamarin Forms!"
                        }
                    }
                }
            };
            var effect = Effect.Resolve ("MyCompany.MyEffect");
            System.Diagnostics.Debug.WriteLine ("effect=[{0}]",effect);
            MainPage.Effects.Add(effect);
        }
    }
}

Notice I am writing the PlatformEffect to the application's output to verify it is resolved. If it doesn't resolve, I should see effect=[Xamarin.Forms.NullEffect].

Here is the applications iOS platform code:

using System;
using System.Collections.Generic;
using System.Linq;
using Foundation;
using UIKit;

namespace EffectTest.iOS
{
    [Register ("AppDelegate")]
    public partial class AppDelegate : global::Xamarin.Forms.Platform.iOS.FormsApplicationDelegate
    {
        public override bool FinishedLaunching (UIApplication app, NSDictionary options)
        {
            global::Xamarin.Forms.Forms.Init ();
            new EffectTestLib.iOS.MyEffect ();

            LoadApplication (new App ());

            return base.FinishedLaunching (app, options);
        }
    }
}

Notice that I am calling new EffectTestLib.iOS.MyEffect (); to be sure my library is loading.

Also, iOS platform project includes a reference to the EffectTestLib.iOS library.

So, when I run the application, this is what happens:

2016-04-06 10:17:18.342 EffectTest.iOS[26578:8696061] effect=[EffectTestLib.iOS.MyEffect]

So, the PlatformEffect is resolved correctly. However, it does not output "Effect Attached" nor throw NotImplementedException. Also note that, if I change a property of MainPage, MyEffect.OnPropertyChanged is never called.

Referring back to https://developer.xamarin.com/guides/xamarin-forms/effects/creating/, it appears I am:

1. Creating a subclass of the PlatformEffect class
2. Overriding the OnAttached method
3. Overriding the OnDetached method
4. Adding a ResolutionGroupName attribute to the effect class.
5. Adding an ExportEffect attribute to the effect class.

And, referring back to https://developer.xamarin.com/guides/xamarin-forms/effects/creating/#Consuming_the_Effect_in_C, it appears that I am adding the effect to the pages Effects collection.

What am I doing wrong here?