Are shadows enabled?

I'm studying Urhosharp and I find it great.

I have now a problem with shadows.
I've downloaded the Samples and for example I see that the shadows are there (Physics example).
If I copy the example in a Xamarin Forms Urhosharp project, then the shadows disappear (Tested on UWP and Android).

The code is exactly the same (Physics demo).
Am I doing something wrong or the shadows are not available in a Xamarin Forms project?

Thanks