Your Paypal Interface is broken

I’ve installed CleanTalk and my key. When I go to our website to subscribe to your premium service, your Paypal interface just runs in a loop, or doesn’t work at all. I log in to Paypal from your checkout page, and then am taken to a different Pay with Paypal screen that looks like it’s a subdomain of Paypal that’s another login. Either the submit button doesn’t work, or it just goes back to the same page.

I’m going to pay via credit card, but I would prefer Paypal. I thought you should know about this problem.

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