Hey there, @Self1
Bo here from Shopify Support!
I am so sorry to hear you are having this issue with your shipping settings, we'll go through some troubleshooting to get this resolved ahead of your launch. What I would like you to check first is where your product inventory is set to. Go to one of your products in the admin and scroll down to the Inventory > Location, take note of where it is set to. Then, go to Settings > Shipping and Delivery and click Manage Rates. Does the product location match the Shipping from location? If not, scroll to the end of the Shipping & Delivery page and add rates to the "Not Shipping from" location listed there.
Once this has all been set up take a look at the conditions for your shipping rates. Does your cart match these conditions? If so, go back to your online store and go through the checkout process once more, and use an Australian address to check out. Let me know how you get on!
If none of this works, please respond to this thread with a screenshot of your Shipping and Delivery Settings and rates and a link to your store so that I can try and replicate this issue. I would highly recommend taking a look at our Help Us Help You post here so that you are better informed on what information to provide when posting a question in the Community.
All the Best,