Payment Page Not Working for Pro Sites


I have been running Pro Sites for 3 years on my site, and recently updated to the latest version of the Pro Sites plugin. As a test, I tried to create a new site and make payment.

When I click subscribe at the bottom of the payment form nothing happens, just refreshes the page. This happens with or without any payment info being entered. I don't even get the red alert boxes if some of the required fields are incomplete, just nothing.

This is kinda urgent since I expect several new signups this week during an annual conversion.