Notification on Samsung Note 9 not working

Question

Android Oreo notification is working fine on emulator but not working on Samsung Note 9. Can anyone suggest me any solution? The notification manager code snippet as follows for Oreo:

NotificationCompat.Builder builder = new NotificationCompat.Builder(this, "channel_id_com_app_android")
.setOngoing(false)
.setAutoCancel(true)
.setSmallIcon(R.drawable.notification_icon_2)
.setColor(getResources().getColor(R.color.accent_color))
.setLargeIcon(convertToBitmap(getApplication().getResources().getDrawable(R.mipmap.ic_launcher)))
.setContentTitle(EmojiUtil.decode(name))
.setContentText(EmojiUtil.decode(message))
.setTicker(EmojiUtil.decode(message))
.setStyle(notiStyle)
.setContentIntent(notificationIntent);
builder.setStyle(bigTextStyle);
builder.setPriority(Notification.PRIORITY_HIGH);
builder.build();

NotificationChannel notificationChannel = new NotificationChannel("channel_id_com_app_android", getString(R.string.app_name), NotificationManager.IMPORTANCE_HIGH);
notificationChannel.setLightColor(R.color.accent_color);
notificationChannel.setLockscreenVisibility(Notification.VISIBILITY_PUBLIC);
NotificationManager manager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);

manager.createNotificationChannel(notificationChannel);