Shows a foreground notification for an Android service. Tapping the notification will display the app as if it was tapped in application launcher

showForegroundNotification.java

 	private static final int NOTIFICATION_ID = 1;

 	private void showForegroundNotification(String contentText) {
		// Create intent that will bring our app to the front, as if it was tapped in the app
		// launcher
		Intent showTaskIntent = new Intent(getApplicationContext(), MyMainActivity.class);
		showTaskIntent.setAction(Intent.ACTION_MAIN);
		showTaskIntent.addCategory(Intent.CATEGORY_LAUNCHER);
		showTaskIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

		PendingIntent contentIntent = PendingIntent.getActivity(
				getApplicationContext(),
				0,
				showTaskIntent,
				PendingIntent.FLAG_UPDATE_CURRENT);

		Notification notification = new Notification.Builder(getApplicationContext())
				.setContentTitle(getString(R.string.app_name))
				.setContentText(contentText)
				.setSmallIcon(R.drawable.ic_notification)
				.setWhen(System.currentTimeMillis())
				.setContentIntent(contentIntent)
				.build();
		startForeground(NOTIFICATION_ID, notification);
	}

Could anyone tell me the possible reasons for foreground service to not show the notification. I have created a channel, started the service using ContextCompat.startForegroundService.