I just tried without a problem – are you using the ‘Embed Code’ from Vimeo or the regular link? (you need to use the embed code I believe with the html extension. Here is what the html extension looks like (I added the <center> tags in front and back manually) the rest is straight from the vimeo-supplied embed code.
<center><iframe src=”https://player.vimeo.com/video/244405542″ width=”640″ height=”360″ frameborder=”0″ webkitallowfullscreen mozallowfullscreen allowfullscreen></iframe>
<p>Happiness from Steve Cutts on Vimeo.</p><center>