Hi,
In your shipping method, I can see that you selected the "shipping australia" zone in the zone restriction. So that shipping method will only appear if the address of the customer is in a sub zone of that "shippinh autralia" zone.
Also, the "AIR" shipping service of Australia Post is only available for customers outside Australia. It's not a limitation of HikaShop or the plugin but the way Australia Post does it.
Standard and Express is for national shipping, and Air and Sea is for international shipping.
take.ms/CQ6GN
If you want cheaper national shipping fees, you need to use "standard".