Change Product Quantity But Shipping Fee not updated

[Halo]

Hi,

I'm using J2.5.16, VM2.0.26. I need some small help/explanation here:

I've setup my product and shipping method. I've tried running or making some mock order through my shop using both registered (with full details) and anonymous user but the problem still persist.

1. Should my customer order only 1 product, the shipping fee will reflect its value. But if I updated the item quantity or make an order in a quantity larger than 1, the shipping fee will not show up. What is the problem & how to solve this?

2. If I order more that 1 type of product, the shipping fee will also not show up? What is the problem & how to solve this?

P/s- sorry for my bad English