Hi Shah,
Did you check if your device is also registrated in the Firebase Middleware? You could check that in the device entity.
Also make sure when sending push notifications to use the original app name instead of the app name from the app identifier. Because special characters will be converted and removed from the app identifier. So in my case I've an app called FirebaseMobile_Project and my app identifier is something like com.outsystemsenterprise.something.FirebaseMobileProject. The problem here is that it won't work like this:

Instead use only FirebaseMobile_Project. So with the special characters and it should work.
Hope it helps.