Hi,
My push notification was working properly but now i'm getting this error {"multicast_id":6149087353033864280,"success":0,"failure":2,"canonical_ids":0,"results":[{"error":"NotRegistered"},{"error":"NotRegistered"}]}

Have you changed something in your store? Something what can have impact on push notifications?

I don't remember but from the error msg, Is it possible to identify?

I would check your Firebase credentials firstly. If they are correct, i would track the changes in the app.