In a flutter application, I want to show notifications to the user by flutter_local_notifications package. This notification appears in the Android emulator, but not in the real mobile device.
This is my source code:

File NotificationManager.dart :

import 'dart:async';
import 'package:flutter_local_notifications/flutter_local_notifications.dart';

class NotificationManager {
  static FlutterLocalNotificationsPlugin? flutterLocalNotificationsPlugin;

  static Initialize() async {
    flutterLocalNotificationsPlugin = FlutterLocalNotificationsPlugin();

    const initializationSettingsAndroid =
        AndroidInitializationSettings('@mipmap/ic_launcher');

    await flutterLocalNotificationsPlugin?.initialize(
        const InitializationSettings(android: initializationSettingsAndroid));
  }

  static Future<void> ShowNotification(String msg, {String title = ""}) async {
    var androidChannelSpecifics = AndroidNotificationDetails(
      'CHANNEL_ID',
      'CHANNEL_NAME',
      //"CHANNEL_DESCRIPTION",
      importance: Importance.max,
      priority: Priority.high,
      playSound: true,
      timeoutAfter: 5000,
      styleInformation: DefaultStyleInformation(true, true),
    );
    var platformChannelSpecifics =
        NotificationDetails(android: androidChannelSpecifics);
    await flutterLocalNotificationsPlugin!.show(
      0, // Notification ID
      title, // Notification Title
      msg, // Notification Body, set as null to remove the body
      platformChannelSpecifics,
      payload: 'New Payload', // Notification Payload
    );
  }
}

main.dart :

...
void main() async {
  ...
  NotificationManager.Initialize();  
    const duration = const Duration(seconds: 10);
    new Timer.periodic(
      duration,
      (Timer timer) {
          NotificationManager.ShowNotification("sample-title", "sample-text");
      },
    );
  Future.delayed(const Duration(milliseconds: 500), () {
    runApp(const MyApp());
  });
}
...

Emulator: Pixel 6 Pro API 31 – Mobile device: Galaxy A22

I tested it on several other mobile devices, but the same problem was seen on them as well.