Embedded video showed as black rectangles on iPhones

Hi everyone
i’m trying to embed some videos. They correctly shows up in Safari and Chrome for desktop, and on Firefox and Chrome for mobile.
Anyway they don’t load on safari for iphones. They are big black rectangles and nothing happes.
What could be the issue?

Published site Brand People Fit
Read only website below:

Here is my site Read-Only: LINK
(how to share your site Read-Only link)