If you receive the error message "Error fetching shipping rates: (400) Invalid input: The API has faced an Unknown Error" when trying to purchase a shipping label with Amazon Shipping, please check through the following:

  • If the shipment is for a non-Amazon order, please check that your Amazon Shipping account has been enabled for External orders (OFF Amazon). This change needs to be made in your Amazon Shipping account itself and not in your Amazon Shipping settings in Shiptheory.

If you need any other help or have any further questions, just reach out to the Shiptheory support team!