Appointments + MarketPress Not Taking You To Payment

Hello,

I have Appointments + installed on our site.

I have the MarketPress integration enabled. However, when you go select a date and time, then enter your information and hit Confirm Appointment, it does not take you to PayPal to complete payment. You can see the page here:

http://www.ifixibuy.com/repairs/products/iphone-4s-charge-port-repair/

Please advise.

Thanks.