"Get Started" button does not appear in welcome screen for FB Messenger bot

I followed the solution in this thread and it is still not working how to setup "Get started" button in facebook messenger bot and when to send welcome message

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

{
  "setting_type":"call_to_actions",
  "thread_state":"new_thread",
  "call_to_actions":[
    {
  "payload":"USER_DEFINED_PAYLOAD"

   }
 ]
}   

The response message is like this

  {
  "result": "Successfully added new_thread's CTAs"
 }

But the message in welcoming screen just keep displaying "Type a message..."

Please help. This is so frustrating. The document on FB developer site is not helpful at all https://developers.facebook.com/docs/messenger-platform/thread-settings/get-started-button

I found the solution. The "Get Started" button does not appear because I used the users who are not "Tester" for my app ( but the Welcome text appeared that why I confused)