.mp4 video clips not visible

.mp4 video clips in a post by @RIL are not visible to me in Chrome on Windows 10. @DavidRutten reports the same problems. I can see them in Edge on Windows 10 and others report seeing them in Safari on a Mac and in Seafoam. The thread with the videos is at GH: Tricky 3D Rotation Angles

Rolf @RIL used a different encoder, h264, and the video is now visible.