PayPal payment button display error

Hello,

Some customers are unable to pay via PayPal on our website, but it worked fine with credit cards, for example.

Here is the error they are encountering (screenshot): https://snipboard.io/KqQPfx.jpg

Normally, the payment button should appear.

What is causing this error and how can we fix it?

Thank you and have a good day.

The page I need help with: [log in to see the link]