There's no message error https://jsfiddle.net/f197cjty/ so I can't see why it doesn't play youtube
<div id="ytplayer"></div>
<script>
// 1. ytplayer code: https://developers.google.com/youtube/player_parameters#IFrame_Player_API
(
function(){
var s = document.createElement("script");
s.src = "http://www.youtube.com/player_api";
var before = document.getElementsByTagName("script")[0];
before.parentNode.insertBefore(s, before);
}
)();
var player;
function onYouTubePlayerAPIReady()
{
player = new YT.Player('ytplayer',
{
height: '390',
width: '640',
playerVars:
{
listType:'playlist',
list: 'RDEMe12_MlgO8mGFdeeftZ2nOQ'
}
});
}
</script>