Sorry to hear about your trouble placing an order. This has happened to me before and can be quite frustrating for sure! First, you want to make sure the order in Shopify has an address in both the billing and shipping settings. If it only has one in billing. you can copy and paste it into the shipping section!
Next, you'll want to make sure you are following these steps when placing the order. Let us know if that helps! If not, I would suggest reaching out to our support team at firstname.lastname@example.org. They can log in and might be able to see something that is causing the error.
Update us on how it goes! I want to make sure it was processed correctly for you.