How to trigger "onNotification" function on received notification?

Question

I am working on react native app and integrated push notification where I used react-native-firebase version 6 and react-native-push-notification package to handle the notifications. But my "onNotification" function is not triggered when getting remote notification. After logged in inside app how can I call the "onNotification" and how it will trigger every time when remote notification occur?

I have created "NotificationHandler" class where I have called "configure" function and created a NotificationService where I called NotificationHandler inside the constructor.

NotificationService::

import PushNotification from 'react-native-push-notification';
import NotificationHandler from './NotificationHandler';

export default class NotificationService{
  constructor(onRegister, onNotification) {
    this.lastId = 0;
    this.lastChannelCounter = 0;

    this.createDefaultChannels();

    NotificationHandler.attachRegister(onRegister);
    NotificationHandler.attachNotification(onNotification);

    // Clear badge number at start
    PushNotification.getApplicationIconBadgeNumber(function (number) {
      if (number > 0) {
        PushNotification.setApplicationIconBadgeNumber(0);
      }
    });
    
    PushNotification.getChannels(function(channels) {
      console.log(channels);
    });
  }
}

NotificationHandler::

class NotificationHandler {
  onNotification(notification) {
    console.log('NotificationHandler:', notification);

    if (typeof this._onNotification === 'function') {
      this._onNotification(notification);
    }
  }

  onRegister(token) {
    console.log('NotificationHandler:', token);

    if (typeof this._onRegister === 'function') {
      this._onRegister(token);
    }
  }

  onAction(notification) {
    console.log ('Notification action received:');
    console.log(notification.action);
    console.log(notification);

    if(notification.action === 'Yes') {
      PushNotification.invokeApp(notification);
    }
  }

  // (optional) Called when the user fails to register for remote notifications. Typically occurs when APNS is having issues, or the device is a simulator. (iOS)
  onRegistrationError(err) {
    console.log(err);
  }
  
  attachRegister(handler) {
    this._onRegister = handler;
  }

  attachNotification(handler) {
    this._onNotification = handler;
  }
}

const handler = new NotificationHandler();

PushNotification.configure({
  // (optional) Called when Token is generated (iOS and Android)
  onRegister: handler.onRegister.bind(handler),

  // (required) Called when a remote or local notification is opened or received
  onNotification: handler.onNotification.bind(handler),

  // (optional) Called when Action is pressed (Android)
  onAction: handler.onAction.bind(handler),

  // (optional) Called when the user fails to register for remote notifications. Typically occurs when APNS is having issues, or the device is a simulator. (iOS)
  onRegistrationError: handler.onRegistrationError.bind(handler),

  // IOS ONLY (optional): default: all - Permissions to register.
  permissions: {
    alert: true,
    badge: true,
    sound: true,
  },

  // Should the initial notification be popped automatically
  // default: true
  popInitialNotification: true,

  /**
   * (optional) default: true
   * - Specified if permissions (ios) and token (android and ios) will requested or not,
   * - if not, you must call PushNotificationsHandler.requestPermissions() later
   */
  requestPermissions: true,
});

export default handler; Inside App.js constructor I have created an object of "NotificationService", it's successfully created token and then I logged in inside app and saved token with the user session. Now after user logged in I want to handle the notifications inside my main screen, I called configure() by creating an object of "NotificationService". I am trying to send test messages using a token from fcm but app is not triggering the "onNotification" function. How we can trigger the main configure "onNotification" function when receives notification?