Keyframe animation not working in WordPress

I am trying to get an animation to run on a pseudo element in wordpress. I cannot work out why it is not working.

However, this animation is working in an CodeIgnite web correctly.

The code is:

CSS:

@keyframes fadeInLeft {
  from {
    opacity: 0;
    -webkit-transform: translate3d(-100%, 0, 0);
    transform: translate3d(-100%, 0, 0);
  }

  to {
    opacity: 1;
    -webkit-transform: none;
    transform: none;
  }
}

.fadeInLeft {
  -webkit-animation-name: fadeInLeft;
  animation-name: fadeInLeft;
}

HTML: <i class="fa-li fa fa-check-square-o wow fadeInLeft" data-wow-delay="1.5s" data-wow-duration="0.4s" ></i>