no links, image, menu is clickable

Hello, I’m coming to you for an unusual site problem. I have already done research in French and English and I have not yet found any leads.
I bought a php script for a site on envato. This script (the site) does not work on all computers.
For me it works very well and for some people, you can’t navigate inside. The site displays well but no links or menus are clickable.
I contacted the seller but I have no feedback.
It’s true that it’s difficult to solve when it works very well at either.
Do you have any early leads? Does it work for you?
My site is not online but the seller has put his site on demo and he has the same problem.
Here is the link I made a video
It’s a really special case and I’ve never had this kind of problem…
Thank you for your insights

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