Debugging notifications

I've been using react-native-fcm for a while. Once in a while it stops working in some specific circumstance. Then, I start changins stuff until it works. I never have full clarity on why I solved it.

This time it's happened again.
I can test Firebase's Notification console to send a notification to a user segment (app) and my device receives it. But if I send it to the specific device id it doesn't work.

How can I got about properly debugging react-native-fcm to figure out where does the problem comes from?