Navigator is not working inside login button

I have to go to Supplier screen when we click login button, i used navigator.push , but it is not working. i used the navigator.push in many other button it is working properly. but for the login its not working.

Padding(
        padding: const EdgeInsets.only(right: 8),
        child: YellowButton(
               label: 'Sign Up',
               onPressed: () {
                        Navigator.pushReplacementNamed(
                           context, '/supplier_home');
                        },
                        width: 0.25),
                            ),

so why it is not working. not understanding, it is inside the scaffold

Make sure the /supplier_home route is declared in your main.dart file using the "routes" property of MaterialApp. And if it is, make sure they're both spelled the same.