Add Facebook Messenger Chat Plugin to HTML not working. We have tried to integrate Facebook Customer Plugin to one of our websites. We followed the instructions in the developer documentation, but it‘s not working.

we use this code after body tag

<div id="fb-root"></div>

<!-- Your Chat Plugin code -->
<div id="fb-customer-chat" class="fb-customerchat">
</div>

<script>
  var chatbox = document.getElementById('fb-customer-chat');
  chatbox.setAttribute("page_id", "102791148828460";
  chatbox.setAttribute("attribution", "biz_inbox";
</script>

<!-- Your SDK code -->
<script>
  window.fbAsyncInit = function() {
    FB.init({
      xfbml            : true,
      version          : 'v12.0'
    });
  };

  (function(d, s, id) {
    var js, fjs = d.getElementsByTagName[0];
    if (d.getElementById(id)) return;
    js = d.createElement; js.id = id;
    js.src = 'https://connect.facebook.net/en_US/sdk/xfbml.customerchat.js';
    fjs.parentNode.insertBefore(js, fjs);
  }(document, 'script', 'facebook-jssdk'));
</script>