If you're booking an order through Amazon or Amazon Buy Shipping and encounter this error, it means the shipment contains multiple parcels. Amazon Buy Shipping does not currently support multi-parcel shipments.
How to Fix It:
Update the order’s box count to 1, then attempt to book the shipment again. This should resolve the issue.
If you are not able to resolve your issue, please contact Support at support@shiptheory.com.
