That message is coming from Amazon when trying to assign the Fulfillment Center (FC) for an item. It could be an item that cannot be sent to that warehouse (oversize, restricted product, etc..) or could be a temporary issue, where their real-time system is timing out and not able to assign the FC (warehouse). Please wait a little while and try to re-list the item. If the error message triggers again please contact Seller Central to inquire about next steps.