Paypal pop up not working on product page

Hi,
I love your plugin, it works everywhere.
However, when I enable Paypal checkout on single product page, the button is showing there on the product page BUT the pop up is not working!
The pop up opens, but nothing is showing inside the pop up.
I read some other people here that had this issue as well.
How is this possible?

Thanks,
Manon van Os

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