Style sheet for iPhone not working

I’ve developed this site co-here.ca and created a child theme based on the parent theme Yoko.

I have adjusted the styles for different media queries. The site loads fine when I use an online iPhone tester, but on an actual iPhone, not only are the styles completely gone, but so are the header, footer, navigation, and sidebar.

I am starting to wonder if the issue is not in the CSS but elsewhere, and have dug around but cannot figure out what the problem is!