title: Facebook Page Messenger not working with Webhook API
body: <p>I followed the steps to setup the Facebook Messenger platform. I have successfully setup the <a href="https://developers.facebook.com/docs/graph-api/webhooks" rel="nofollow noreferrer">webhook</a>, I receive messages on my webhook.
  For webhooks to work, I obviously had to subscribe my page, see the screenshot.
  <a href="https://i.stack.imgur.com/TMzP3.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/TMzP3.png" alt="enter image description here"></a></p>
  
  <p>Now the strange problem is, if I keep my page subscribed to a webhook, my facebook page messenger doesn't show any thing.
  As soon as I unsubscribe my page for webhook, page messenger nicely loads.
  <a href="https://i.stack.imgur.com/7vuaX.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/7vuaX.png" alt="enter image description here"></a></p>
  
  <p>What can I do ?</p>