Integrating a standard Paypal checkout in PHP

I have a PHP script which I've got working with Paypal checkout but the only issue I've got is it doesn't seem to work with IOS device such as Apple macs and IPADS and sometimes with certain Android devices.

I have contacted Paypal and they said it's a device security issue nothing to do with Paypal which am not sure about.
The error message am getting is "Things don't appear to be working at the moment. Please try agan later".

Also I got a video showing the error. It works fine on windows and some other devices .

zoomparcel.co.uk/video/WhatsApp Video 2021-04-12 at 15.35.10.mp4