Firebase messaging not working [Not receiving notfications] but app connected to Firebase

I was following a tutorial for firebase push notifications, I followed all the steps: Connecting the app to firebase, importing packages (Firebase messaging and Firebase push notifications), I tried sending several notifications but it did not work.

I know my app is connected to firebase as I am receiving data from cloud firestore and authentication also works and I am also able to write data to storage :

My main.dart:

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp(
    // Added actual values
    options: const FirebaseOptions(
      apiKey: "have added this ",
      appId: "have added this",
      messagingSenderId: "have added this",
      projectId: "have added this",
      storageBucket: "have added this",
    ),
  );
  runApp(const MyApp());
}

class MyApp extends StatefulWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  @override
  void initState() {
    super.initState();

    FirebaseMessaging.instance
        .getInitialMessage(); /this helps code below work great

    FirebaseMessaging.onMessage.listen((message) {
      if (message.notification != null) {
        print(message.notification!.body);
        print(message.notification!.title);
      }
    }); 
    FirebaseMessaging.onMessageOpenedApp.listen((message) {
     
      final routeFromMessage = message.data['route'];

      print(routeFromMessage);
    });
  } 

  @override
  Widget build(BuildContext context) {
    return ChangeNotifierProvider(
      create: (context) => GoogleSignInProvider(),
      child: OverlaySupport(
        child: MaterialApp(
            title: 'News_App_admin',
            theme: ThemeData(
              buttonTheme: const ButtonThemeData(minWidth: 80),
              primarySwatch: Colors.blue,
              secondaryHeaderColor: const Color.fromARGB(255, 75, 177, 78),
            ),
            home: // MyHomePage(title: 'Home page'),
                StreamBuilder(
              builder: (ctx, userSnapshot) {
                if (userSnapshot.hasError) {
                  Center(
                    child: Text('Unknown Error'),
                  );
                }
                if (userSnapshot.hasData) {
                 
                  return bottomNavigationBar();
                }
                return const Auth_Screen();
              },
              stream: FirebaseAuth.instance.authStateChanges(),
            ) 
  }
}