The error "Unable to create label Error confirming shipment: The selected service is not available from the origin to the destination (121210)" is an error UPS sends back for one of two reasons;
The first reason why this error may occur is that the address for the shipment isn't valid, this would mean that UPS wouldn't be able to deliver the shipment and so they reject it before it can be booked in.
The second reason why this error may occur is that the service you have selected is not available for the destination of the shipment, you will need to select an alternative service that is available for the destination of the shipment.