Pro Sites PayPal redirect doesn't work

If I only offer one payment period (annually), when I click the PayPal button to process the payment, it redirects to the same page. If I add a monthly payment period option, the PayPal button works as expected.

Here's a link to where the problem is occurring: http://myfoley.com/pro-site/

I only want to offer annual billing, but that doesn't seem to be working at the moment.