Thecartpress help Please :)

When i add to cart and try to proceed to checkout it will say i have no items in my cart? It also does the same thing when i try to check out. Please look at my site any advice would be greatly appreciated. If someone with a similar experience would tell me what they did to resolve this issue. I would appreciate any help. thank you

http://www.hartannsoul.com/

http://wordpress.org/extend/plugins/thecartpress/