Q:

How to send notification to any device when it goes online?

I remark that when I send a message using FCM only the online devices receive the notification is there any way to send to all Devices ( the online devices and the other devices when they go online)?

A:

I posted these on your request these are the implementation :
part 1 Firebase part
part 2 One Signal Part
part 3 One Signal Part Completion ( 2 minutes)
I think you have done part 1 since you told that you have integrated firebase but you can check them and please if it worked for you accept my solution thank you so much :) .

