Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
Since you’ve already confirmed the account, billing address, and sign-in, the usual leftover cause is an old payment method or a leftover cache. Open account.microsoft.com, go to Payment & billing, and remove any saved cards or PayPal accounts tied to another country, then add your Australian one again as the default. Also check Windows Settings, Time & language, Language & region, and make sure “Country or region” (not just “Regional format”) says Australia, then restart.
After that, press Win + R, type wsreset.exe, and hit Enter to clear the Store cache, and turn off any VPN