Hi,
Well, I can't say much without more information. First, is the Australia Post v2 shipping method showing up during the checkout with the same address ?
If yes, then we would need to investigate the situation and we'll need a backend access and a FTP access to check what's going on.
If no, then the problem is with the setup of the product / shipping method and it is not linked to the shipping estimation plugin. Probably, you forgot to add weight/dimensions in the product, or maybe an issue with the settings of the shipping method.