[Database#on](https://github.com/fullstackreact/react-native-firestack/blob/master/lib/modules/database.js#L405) is not supporting setting cancel callbacks. This makes it impossible to deal with Permission Denied errors. Currently, on error the library will simply log the error message. (https://github.com/fullstackreact/react-native-firestack/blob/master/lib/modules/database.js#L401) See [Firebase documentation](https://firebase.google.com/docs/reference/js/firebase.database.Query#on).