Vimeo Videos in Responsive Design

jfrench5556 Community Member Posts: 17
Our videos are all on Vimeo, so I'm displaying them using an HTML extension. They work great in a standard (non-responsive) course, no matter what kind of display we're using, including all the phones we've tried. But when I make the course responsive, there's a problem. They look fine on my iPhone 8 (version 12.1.2), and on my colleague's iPhone 6S (version 12.1). However, they never show up at all (no video, no frame) on my other co-workers' iPhone X, iPhone XS Max (version 12.3.1), or iPhone 7 Plus. (They're published as SCORM modules on a moodle platform). Any ideas?