Hi,
This indicates a problem of HTTPS authentication with paypal.com's server I think.
Basically, it looks like PayPal is refusing the connection between the security protocol used by the browser for the HTTPS communication is too weak for their new criteria.
That's what I'm guessing since I'm not working at PayPal and thus can't check the logs of that payment request.
The best is to contact the PayPal support and provide them with the error message and the reference in the screenshot so that they can check what is wrong.
I highly suspect that the problem cannot be solved by changing something in HikaShop or even in the settings of HikaShop, but that the problem might be with the browser of the user, especially since it still works for everyone else.