I recently updated Xamarin. Ever since that time, I have been unable to build my iOS application due to this error:
Your application is using the 'HealthKitUI' framework, which isn't included in the iOS SDK you're using to build your app (this framework was introduced in iOS 9.3, while you're building with the iOS 9.2 SDK.) This configuration is only supported with the legacy registrar (pass --registrar:legacy as an additional mtouch argument in your project's iOS Build option to select). Alternatively select a newer SDK in your app's iOS Build options.
Has anyone else seen this? I haven't changed anything in my code.
Looks like you need to upgrade to Xcode 7.3. Could you perform that update and let us know?
iOS 9.3 requires Xcode 7.3 support, these were added in Xamarin.iOS 9.6.0.0: https://releases.xamarin.com/stable-release-ios-9-3-xcode-7-3-support/
Also, check out the following for information on iOS SDK releases against Xcode releases.