[Fixed]-Notification received but no icon displayed in notification bar

Could be two reasons

1. Is your app in the background when receiving it? Check https://firebase.google.com/docs/cloud-messaging/android/receive

2. Also based on the above link, only under two situations, your device will automatically show your message as a notification. The message might be delivered to your app, where your app will then need to push a notification to the device. Check https://developer.android.com/training/notify-user/build-notification.html