Can't add additional boxes with shipping?

I'm using the Canada Post shipping module.
I'm probably just missing a setting somewhere, but I can't seem to have it add additional boxes for larger orders.

Someone is trying to order multiple copies of an item and it only ever tries to put them in 1 box, and although it's a large box, it won't fit them all and instead of adding a 2nd box, it simply doesn't do anything and brings back a blank page with no shipping results except local pickup -_-

So any ideas of what setting I have wrong?