there is a known issue with Firebase SDK with iOS 11 (search https://github.com/firebase/quickstart-ios issue number 327)
fix is `pod 'FirebaseInstanceID', "2.0.0"`

Before openning an issue
1. Reproduce it with the example project in this repo.
2. If you can't receive iOS notification, make sure you can receive notification using quickstart-ios project provided by Firebase team

When openning an issue, please include following information for better support

1. What version of RN and react-native-fcm are you running?
2. What device are you using? (e.g iOS9 emulator, Android 6 device)?
3. Is your app running in foreground, background or not running?