keyframes animation not working in ie11 after ajax call, works fine in ie10

Question

I've been fighting with this issue all morning: I have a simple keyframes animation that works fine in chrome, safari, firefox and ie10, but with ie11 it doesn't work, or at least not after an ajax call. The animation works perfectly if I place it in the main body of the page, but stops working if I place it in the returned html of an ajax call. here's my code:

<div class="ie-animation-test">
    test
</div>


.ie-animation-test {
  position: absolute;
  background: red;
  top: 0;
  left: 0;
  z-index: 999999999;
  animation: 3s infinite ie-anim-test ;
}

@keyframes ie-anim-test {
  0% {
    top: 0;
    left: 0;
  }

  50% {
    top: 200px;
    left: 200px;
  }
  100% {
    top: 400px;
    left: 0;
  }
}