Error 21916250: A return option is missing or not valid. Update your return options.

This error is returned if the ReturnPolicy container is missing, or if it is included, but the existing information in that container is invalid. The ReturnsAcceptedOption field must be set, and if it is set to ReturnsAccepted, the RefundOption, ReturnsWithinOption, and ShippingCostPaidByOption fields must also be set. The International return policy fields only have to be set if the seller ships internationally and that seller uses a different return policy for international buyers.