Dialogflow webhook TypeError: Cannot read property 'Parameters'

Question

I'm Using Dialogflow with Firebase and the V2 API, I'm getting this error on my webhook:

TypeError: Cannot read property 'parameters' of undefined
    at exports.dialogflowFirebaseFulFillment.functions.https.onRequest (/srv/index.js:15:38)
    at cloudFunction (/srv/node_modules/firebase-functions/lib/providers/https.js:49:9)
    at /worker/worker.js:783:7
    at /worker/worker.js:766:11
    at _combinedTickCallback (internal/process/next_tick.js:132:7)
    at process._tickDomainCallback (internal/process/next_tick.js:219:9)

I've already looked this post, but I cannot figure any difference between his line and mine.

This is the code:

const functions = require('firebase-functions');

process.env.DEBUG = 'dialogflow:debug';

const admin = require('firebase-admin');
admin.initializeApp();

exports.dialogflowFirebaseFulFillment = functions.https.onRequest((request, response) => {
  console.log('Request headers: ' + JSON.stringify(request.headers));
  console.log('Request body: ' + JSON.stringify(request.body));

  const parameters = request.body.queryResult.parameters;
  const db = admin.firestore();

  const reservationRef = db.collection('reservations').doc('room-reservation');
  reservationRef.add(parameters).then(() => {
    response.send({
      speech: 'Room reserved!'
    });
  }).catch((e => {
    response.send({
      speech: 'something went wrong'
    })
  }))
});

Is the error anywhere else? Thanks.

EDIT: Actually none of the console.log's are showing.

My webhook is being triggered from the cloud function url. I've already provided it:

When browsing that url it says: Error: could not handle the request, but I suposse it is normal as I haven't provided any params. Is that correct?

Do I have to provide authentication when configuring the webhook?

EDIT 2:

This is the log (Couldn't find it, my mistake):

The error in the log is the same as the one I mentioned starting.