There is a guide how to track notification delivery status per message_id or device token:
https://support.google.com/googleplay/android-developer/answer/2663268?hl=enbut on FCM diagnostics page there is alert:
> FCM diagnostics page to be removed
> From Nov 20 2017, the FCM diagnostics page will be removed along with any historical data. However, you can continue to access other Firebase Cloud Messaging features on the Play Console.
Currently FCM diagnostics page is not usable...
How can I found notification delivery status by message_id?