When you send a chat message and the recipient is offline, then an automatic push notification will be fired. To receive push notifications you need to subscribe for them. Please refer to Push Notifications guide.To configure push template that users receive, go to Dashboard => YOUR_APP => Chat => Offline messaging.
FCM data messages can be sent to the Android app. QuickBlox doesn’t support FCM notification messages.To process FCM data messages on your app when the app is in the background, you need to handle them. If not handled, they will not pop on the screen even if the app has received such push notification. See FCM documentation to learn more about data messages.
Currently, push notifications are supported in a mobile environment only.