The message "Please fill your company's billing address in Shopify store's settings" indicates that Shopify requires your company's billing address to be entered into the system for the order fulfillment process to proceed.
This happens for a variety of reasons, such as:
Payment Processing: The billing address might be required for validation during payment processing.
Tax Calculations: Shopify and Selfnamed need the address for accurate tax calculations.
Legal Requirements: It is also a legal mandate to have the billing details on record.
Go to Shopify Settings: Log in to your Shopify admin and navigate to the 'Settings' menu.
Update Address Information: Under 'Settings', look for 'General' or 'Billing' to fill in or update your company's billing address.
No Empty Fields: Ensure that no fields are left empty. If a certain field is not applicable, you can use a placeholder like "-" instead.
Save Changes: Make sure to save any changes made.
Verify Update: Confirm that the new address information is correctly displayed.
Test Fulfillment: Try processing an order to see if the issue is resolved.