It might be because the checkout process is a little confusing. when I went to the order page it says at the top Step one "Select Product" I click on the product because that's what I think select product means and then there's no buy now button when the large image shows. That will make me leave the site because I don't think you're open for business.
Possible suggestions would be to change the the text from "Select Produt" to "Enter Quantity" and make the step 2 button visible also at the top of the page because I had to search for the step 2 button.
Another suggestion is use the conventional order method
1. Click the item to show details
2. On the details page the user can add as many items to the cart as needed.
3. They can checkout from here or continue shopping.
Hope this helps
bDoc
www.datamatrixit.com