How to call from Nested UserControl another UserControl

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WPF

Hello Everyone

I'm struggling to solve the problem with my nested UserControl.

When I run the application the main window opens, inside the main window is a button, when I click that button it calls up a UserControl (called Applic).

Inside the Applic UserControl is another nested UserControl called PasswordScreen.

Within the PasswordScreen there is a button called Login, when I press this button to call another UserControl (called SwitchboardView) it is not firing nothing (here is the sample code)

private void btnLogin_Click(object sender, RoutedEventArgs e)
        {
            Applic ap = new Applic();
            SwitchboardView sbv = new SwitchboardView();
            
            ap.MainGridApplic.Children.Add(sbv);

        }

Could someone please help me solve this problem, I have been struggling for a long time to solve this problem but I just can't get it around.

Thanks in advance...

Kind regards

Roni