There is a bug in Shipstation when using the GlobalPost carrier. Shipstation returns a valid GlobalPost rate when entering box dimensions of 41" X 16" X 16" and weight of 37 pounds for a shipment from the USA to Australia. However trying to purchase a label will return an error. This is due to the fact that GlobalPost box size is Max L: 24" and L+W+H < 36". Shipstation should not return a rate at all even before purchasing the label. I had to cancel orders with Australian customers because I was unable to purchase labels due to this Shipstation bug.