Tone.Sequence not running on iOS

<!DOCTYPE html>
<html>
<head>
  <meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1, user-scalable=no">
  <title>StartAudioContext</title>
  <script type="text/javascript" src="StartAudioContext.js"></script>
  <script type="text/javascript" src="Tone.js"></script>
</head>
<body>

.starterButton:active {
    background-color: #FFB729;
    color: white;
  }

span {
    font-size: 16px;
    margin-right: 5px;
    font-family: monospace;
  }

</style>

<span>STATUS:</span><span id="isStarted">NOT Started</span>

<div class="starterButton">Tap to start the AudioContext</div>
  <div id="tonedebug"></div>

//create an audio context
  window.AudioContext = window.AudioContext || window.webkitAudioContext
  var audioContext = new AudioContext()

//set the context
  StartAudioContext(Tone.context, ".starterButton").then(function(){
    document.querySelector("#isStarted").textContent = "Started";
    Tone.Transport.start();
    seq = new Tone.Sequence(function(time, note){
        document.querySelector("#tonedebug").textContent = note;
    }, ["C4", ["E4", "G4"], "A4"], "4n");
    seq.start();
  })

</script>
</body>
</html>