Break point hollow and cant step into Method

Hi there,

I have the following code:

public partial class LoginOrRegister : ContentPage
{
public LoginOrRegister ()
{
InitializeComponent ();
}

    protected override void OnAppearing ()
    {
        RegisterWithFacebook();
    }

    private void RegisterWithFacebook() {
        string data = FBRepository.DoStuff ("asdasdasd");
    }
}

public class FBRepository
{
public static string DoStuff( string stuff) {
return stuff + DateTime.Now.ToString();
}
}

This code is sitting in the shared code project, and its for iOS only. I have the latest version of Xamarin.
Any idea why the breakpoint is hollow, and why I cant step into the method?

The code runs fine, in that the DoStuff will return the expected result.

Thanks,
David