Your theme is setting CSS styling to the audio and video HTML5 tags, which has negative effects on how the player will appear in older versions of iOS. The older versions of iOS show a very thin and narrow player, it's disgusting looking, but nearly impossible to style with CSS, and anything that tries to modify the audio/video via CSS for those older versions of iOs usually do more harm than good.
So in your CSS for your theme, remove audio and video in the comma separated list of styles at the top, then see if it appears. don't forget to clear your browser cache after you modify your theme.