Hi there,
When I check your site and click on the PayPal option on the cart page, I do see the PayPal window opening up properly: https://d.pr/i/C6EAr1
And this is what happens when I am clicking on the Debit or Credit card: https://d.pr/i/iWmSnF
I tried these steps as a guest on your site and it seems to be working on my end. Did you manage to resolve the issue or does it still persist? If it still happens, could you please let us know what steps you are taking on the site to trigger the issue e.g. are you trying to do a checkout from the cart or checkout page or so? Thanks!