@Chdid is the curl command actually send a push notification to your Android phone?
Do you have a basic sketch where the push fails? Sometimes the problem is a bad loop where users accidentally try to send more frequently than the permitted one message every 15 seconds (was previously one per minute).
I only use notifications with the HTTP API, with nodered, at a rate of 2 to 6 per day.
1 post at a time on 2 android.
The server is installed on a raspberry3 and the notifications worked correctly until 15 days ago.