Hello Debbie,
Great question. I believe it’s a file format issue. If I view the page in Safari the video does not show, just like it doesn’t on my iPad. It looks like the page is using a webm video. If I view the page in Chrome, which supports that format, it is visible there.
What you may want to do is use the video shortcode with all three file formats listed: mp4, webm and ogg. The Codex entry for the shortcode at https://codex.wordpress.org/Video_Shortcode can show you how to format it that way.
If I’m only listing one video type, I usually just go with mp4 as that’s worked well in the past for me.
That said, I’ve always had best success using Vimeo to host and stream my videos. They handle all the heavy lifting for me and I’ll have to do is insert the URL to the video page on their site into my page/post content and it just works. YouTube also has that ability too.
Take care,
Bill