Video not working/playing on some of the older versions of iphone but works on mine (iphone 11 pro max) and android

Hello, badly need your help on this. the video on the mobile mockup in the site is working on desktop, android but not on all versions of iphone. It works fine on my end (iphone 11 pro max) but the video does not play on my brother’s iphone 6+

does anyone have an idea how to fix this issue?

Will highly appreciated your help. Thank you so much!!

This may be something you can’t control. Until recently, video would not auto play at all on any smartphone because of battery and performance issues.

The limitation was progressively lifted but it it possible that iOS still prevents it for older devices.