Constant Error Popup

I’m constantly getting an error popup when adding items to cart or on checkout page, saying “Australia Post Live Rates: Please enter To postcode.”

Obviously once I go thru the checkout process and add the postage address the error goes away since now it’s got the “To” postcode. But I don’t want this being displayed to my customers!

How can I get rid of it?

Or overwrite it to have a default postcode until altered by the customer at checkout? It’s so frustrating, I’ve tried everything