It's actually an implementation issue and yes, I agree it's unfortunate. The problem is that the video is rotated in 3D in CSS (so we can reuse the same video without the fancy 3D effect on smaller displays since the page is vertically responsive) and unfortunately, the result varies depending on the browser (it looks much better on Safari, for example).

Ditto with Firefox 38.0.5 on OS X 10.10.3.

First time I've had any disappointment in a Stripe design. Their stuff has been solid.

Chrome on iPad in landscape shows the phone, non-tilted, with just a black screen. I had to check the screenshot someone else posted to see what it should look like. In portrait, the phone is tilted but still nothing displays on the phone.