How to Make Video Work On Mobile?

As you can see in the first image the video is correctly being shown:

But in the mobile version it doesn't show the poster. It just shows a play button. And then even if I click the play button nothing happens:

How can I make the video mobile version look like the desktop version? I'd like their to be a poster image with a play button over it and then when play button is clicked it plays.

HTML

<video style="width:40%; display:block; margin:0 auto;" controls>
  <source src="/assets/fake-prince.m4v" type="video/mp4">
</video>