Function not recognizing when embedding videos

API
3 
<html>

<!-- Load the Twitch embed script -->
<script src="https://embed.twitch.tv/embed/v1.js"></script>

<!--
  Create a Twitch.Embed object that will render
  within the "twitch-embed" root element.
-->
<script type="text/javascript">
  var embed = new Twitch.Embed("twitch-embed", {
    width: 854,
    height: 480,
    channel: "monstercat",
    layout: "video",
    autoplay: false
  });

  var player = embed.getPlayer();
  player.addEventListener(Twitch.Player.PLAY, function() {
    changeAdvertisementBanner();
  });
  player.play(); 
</script>

Taken from here