title: Facebook messenger webhook won't receive any messages
body: <p>I created a webhook for facebook, the subscription worked fine, (See the JSon result below). But whenever i send a message to the page, the webhook doesn't receive anything, the only entries from the webhook that i receive is when i subscribed to the page.</p>
  
  <pre><code>{
     "data": [
        {
           "object": "page",
           "callback_url": "https://{MY_DOMAIN}.nl/facebookmessenger/webhook/index.php",
           "fields": [
              "conversations",
              "message_deliveries",
              "messages",
              "messaging_account_linking",
              "messaging_optins",
              "messaging_postbacks"
           ],
           "active": true
        }
     ]
  }
  </code></pre>
  
  <p>I know for a reason that the webhook page itself works. So i don't feel the need to add it here.</p>
  
  <p>If there's anything else you need to ask, you're free to ask</p>