OnAppearing not getting invoked

Hi,

I have the following OnAppearing in my Signup page..

protected override async void OnAppearing()
{
        .............
        .............
        .............
}

From HomePage, the user clicks add and if the user is not signed in then t will start the Signin ContentPage like this:

Navigation.PushModalAsync(new NavigationPage(new Signin())
{
    BarBackgroundColor = Color.White,
    BarTextColor = Color.Black
});

From the Signin Page the user clicks on the Signup button which will start the Signup ContentPage like this:

Navigation.PushModalAsync(new NavigationPage(new Signup())
{
    BarBackgroundColor = Color.White,
    BarTextColor = Color.Black
});

so then anything I keep in the OnAppearing will NOT be invoked even just a simple:

await DisplayAlert("Signup", "OnAppearing should start", "OK");

I am using Xamarin Forms 3.6.0.293080

Kindly help..

Thanks,
Jassim