Shipping only caluculates one product?

Hi,

We are using wp-ecommerce with the’Australia Post’ add-on to calculate shipping charges.

Everything is working correctly with the exact amount of shipping being calculated – but it only calculates and adds shipping for one product?

If a customer buys more that one product the additional product[s] have no shipping added.

What settings do I need to change in order to have shipping calculated and added to all products purchased?

Thank you

https://www.ads-software.com/plugins/wp-e-commerce/