Hi, @PacificBlue !
Thanks for getting back to me. The error is likely occurring because of non-English characters in your store settings, not the domain itself. If your store address contains a character like “ß” or “Å”, this would affect the purchase of the domain, since OpenSRS has specific billing information requirements. I recommend logging into your Shopify admin and navigating to Settings > Store details to verify whether there are any special characters in your address or name. If there are, you can replace those characters with their English counterpart (for example, straße should be strasse).
Let me know if you’re able to make those changes and purchase the domain!