Everything looks fine here
</head>
<body style="font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;">
<div id="app" class="full-height"></div>
<script src="https://extension-files.twitch.tv/helper/v1/twitch-ext.min.js"></script>
should be
<script src="https://extension-files.twitch.tv/helper/v1/twitch-ext.min.js"></script></head>
<body style="font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;">
<div id="app" class="full-height"></div>
Technically. But its working on my screen with no relevant console errors