Same problem. I found out it’s my loading sequence problem, because I write CSS inline and then I call respond js script, so it looks like
<script type="text/javascript" src="https://stackoverflow.com/questions/15127040/js/respond.min.js"></script>
<link rel="stylesheet" type="text/css" href="https://stackoverflow.com/questions/15127040/style.css" media="screen" />
It should be
<link rel="stylesheet" type="text/css" href="https://stackoverflow.com/questions/15127040/style.css" media="screen" />
<script type="text/javascript" src="https://stackoverflow.com/questions/15127040/js/respond.min.js"></script>
ALWAYS link stylesheets or write inline CSS before js scripts!