Troubleshooting Amazon Shipping Error: S-900

If you encounter the following error when trying to book an order with Amazon Shipping:

"Error Fetching Shipping Rates: (400) Invalid input: We apologize for the inconvenience. We cannot ship the order due to an internal service error. Please contact us for additional support. (S-900)."



This issue can be caused by missing product weights for the SKUs in the order.

How to Fix It:

  1. Check the SKUs in the order and ensure each one has a weight assigned.
  2. Update the product weights in your system.
  3. Try booking the order again.


Once the weights are updated, the order should process successfully. If you have any questions regarding this or anything else, please don't hesitate to get in touch with the Shiptheory support team!