Shopping Cart Appears Empty on Check Out

Hello,
I just updated wordpress and some plug ins and made the mistake of not backing up.
When customers go to my website http://www.burningpassion.com and add items to their shopping cart, when they go to check out their cart appears empty.

I’m losing sales over this, it’s hurting bad. How can I fix this?
Thank you SO much!
Paul

https://wordpress.org/plugins/wp-e-commerce/