title: "Get Started" button does not appear in welcome screen for FB Messenger bot
body: <p>I followed the solution in this thread and it is still not working 
  <a href="https://stackoverflow.com/questions/38048224/how-to-setup-get-started-button-in-facebook-messenger-bot-and-when-to-send-wel">how to setup &quot;Get started&quot; button in facebook messenger bot and when to send welcome message</a></p>
  
  <p>I tried both 
  graph.facebook.com/v2.6/me/thread_settings?access_token=xxxxx
  and 
  graph.facebook.com/v2.6/page_id/thread_settings?access_token=xxxxx
  with the raw body </p>
  
  <pre><code>{
    "setting_type":"call_to_actions",
    "thread_state":"new_thread",
    "call_to_actions":[
      {
    "payload":"USER_DEFINED_PAYLOAD"
  
     }
   ]
  }   
  </code></pre>
  
  <p>The response message is like this </p>
  
  <pre><code>  {
    "result": "Successfully added new_thread's CTAs"
   }
  </code></pre>
  
  <p>But the message in welcoming screen just keep displaying "Type a message..."</p>
  
  <p>Please help. This is so frustrating.  The document on FB developer site is not helpful at all 
  <a href="https://developers.facebook.com/docs/messenger-platform/thread-settings/get-started-button" rel="noreferrer">https://developers.facebook.com/docs/messenger-platform/thread-settings/get-started-button</a></p>