OnPlatform Tweek not working for Windows Phone

Hi Guys,

I am new here so may have an issue with code, but the following is not working as expected

<BoxView.BackgroundColor>
        <OnPlatform x:TypeArguments="Color"
          iOS="Green"
          Android="Red"
          WinPhone="White" />

      </BoxView.BackgroundColor  >

On the windows Phone emulator and physical device the box view is green, or what ever colour I set it to. It is correct on android. I think the code thinks the device is IOS and not windows phone. any Ideas?