The error “120598: Package Delivery Confirmation is not allowed with the shipment origin/destination” indicates that the delivery confirmation option selected is not compatible with either the origin or destination of the shipment as per UPS’s policies.
To address this, please verify the shipping services and options available for the specific origin and destination by using the UPS rate calculator here: https://wwwapps.ups.com/ctc/. This will help confirm if the service is indeed available for the addresses in question.