Exception while loading assemblies: System.IO.FileNotFoundException: Could not load assembly 'Microsoft.Windows.Design.Extensibility, Version=126.96.36.199, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'. Perhaps it doesn't exist in the Mono for Android profile?
If you updated the nuget packages for Xamarin Forms to 2.0+ and the android project stops to build there are a simple solution. Just delete the references which ends with .Design. In my project it was: Xamarin.Forms.Core.Design, Xamarin.Forms.Xaml.Design and Xamarin.Android.Support.Design. I have read about a solution to add the assemblies Microsoft.Windows.Design.Extensibility and System.Xaml. I don’t know if it will work, I think to delete the .Design references is a better solution so I never tried to add those assemblies.