title: I am having issues with Twilio Sync and ReactJS and page is not updating while I send SMS
body: <p>I am setting app a chatbot with Twilio and ReactJS, barista order bot, I am not able to display my messages real time on browser. I create a React app so I can display every time I send a SMS then it will also display on browser. </p>
  
  <p>I went to Twilio console and tried to see if maybe I need to modify my function where the sync occurs. </p>
  
  <p>This is the token function created.</p>
  
  <pre><code>exports.handler = function(context, event, callback) {
    const ACCOUNT_SID = context.ACCOUNT_SID;
  
    const SERVICE_SID = context.SYNC_SERVICE_SID;
    const API_KEY = context.API_KEY;
    const API_SECRET = context.API_SECRET;
  
    const IDENTITY = 'barista';
  
    const AccessToken = Twilio.jwt.AccessToken;
    const SyncGrant = AccessToken.SyncGrant;
  
    const syncGrant = new SyncGrant({
      serviceSid: SERVICE_SID
    });
  
    const accessToken = new AccessToken(ACCOUNT_SID, API_KEY, API_SECRET);
  
    accessToken.addGrant(syncGrant);
    accessToken.identity = IDENTITY;
  
    const response = new Twilio.Response();
  
    const headers = {
      'Content-Type': 'application/json',
      'Access-Control-Allow-Origin': 'http://localhost:3000',
      'Access-Control-Allow-Methods': 'GET',
      'Access-Control-Allow-Headers': 'Content-Type'
    };
  
    response.setBody({ token: accessToken.toJwt() });
    response.setHeaders(headers);
  
    callback(null, response);
  };
  
  </code></pre>
  
  <p>I get these two errors on my browser</p>
  
  <pre><code>Access to fetch at 'https://goldenrod-labradoodle-4220.twil.io/barista-token' from origin 'http://localhost:3000' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.
  </code></pre>
  
  <pre><code>orders.js:26 GET https://goldenrod-labradoodle-4220.twil.io/barista-token net::ERR_FAILED
  </code></pre>
  
  <p>Any help, greatly appreciated.</p>