Firebase RTDB trigger not fired from Flutter Firebase SDK triggering event

Question

I am developing an application in Flutter and during development, I encountered this anomaly.

On Firebase Realtime Database I have a simple trigger for testing the functionality, the trigger is this:

/**
 * Triggered by a change to a Firebase RTDB reference.
 *
 * @param {!Object} event Event payload.
 * @param {!Object} context Metadata for the event.
 */
exports.helloRTDB = (event, context) => {
  const resource = context.resource;
  // log out the resource string that triggered the function
  console.log('Function triggered by change to: ' +  resource);
  // now log the full event object
  console.log(JSON.stringify(event));
};

(Function name: createGame)

Function to execute: helloRTDB

Trigger type: Firebase Realtime Database (beta)

Event type: create

Database: my-db

Path: /lobby/{userId}

When I run this from Cloud Functions Testing on Google Cloud Platform works well but this does not work when I run the triggering event from Flutter - Firebase Database SDK.

Cloud Functions Testing:

Flutter - Firebase Database SDK:

class FirebaseLobbyRepository {
  final lobbyCollection = FirebaseDatabase.instance.reference().child('lobby');

  Future<void> test() {
    return lobbyCollection.set('test'); // This work but attached trigger not.
  }
}

When I call test() method the record is added in the RTDB but the trigger is not fired! Why?

Thanks for the help.