InheritedWidget - The getter was called on null after navigator.push

InheritedWidget should wrap the full MatrialApp widget (root widget)

In the code you've provided, LoginScreen is not a descendant of LoginBlocProvider which is why it can't find the ancestor widget. Your code wraps the WelcomeScreen route in LoginBlocProvider, but not the whole navigator. The solution is to wrap your MaterialApp in LoginBlocProvider and then you will have access to it everywhere in your app.

class App extends StatelessWidget {
  @override
  Widget build(context) {
    return LoginBlocProvider(
      child: MaterialApp(
        title: 'Iniciar Sesion',
        home: WelcomeScreen(),
      ),
    );
  }
}