Cloudflare Stream MP4 Thumbnail not loading on Safari (iOS + OSx)

I have been tested the thumbnails to make our website to be more animated. However, if I am using mp4 thumbnail the video is not loaded on safari. The following is the link and I tested it by opened it directly with Safari. Please advise how to solve this problem.

https://community.cloudflare.com/search?q=ios%20mp4

Hi @sandro,

None of them are using Cloudflare Stream. Is there something I can control at the videdelivery.net?

Thank you,
Szelee