We have observed that a few customers may encounter such an error at checkout, especially for Apple Pay and Shop Pay users, even though your country is supported.
Here's how to resolve. Revisit your checkout session. When you encounter the error again, click on "Change" beside your address:
Then check your state/county/province. You may see it is unselected, which is the cause for the error. Simply re-select your correct state/county/province:
Do check your address once more. You should now be able to complete your checkout.
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