flutter routing not routing

Question

I'm building an amazon clone app, currently building the sign up function of the app. I run into the following problem is when I as a user sign up for an account and click on sign up there happen's nothing. How the code is setup it should reroute back to the sign in page:

this is the code:

`Navigator.pushReplacement(
                                        context,
                                        MaterialPageRoute(
                                            builder: (_) =>
                                                const SignInScreen()));

There happens litteraly zero. It should route from the sign up page to the sign in page but doesn't do that.

I tried creating a route from a sign up button back to a sign in screen with the use of MaterialPageRoute to the SigninScreen. It loads for a second then stops and stays in the same sign up screen. While still adding the account to the firebase database.