UPS Canada to US
I am looking to ship an order from Canada to US via UPS Ground and the error that I receive when I generate the multiple labels is "Package/ReferenceNumber is not allowed for this shipment" This is the first multi piece shipment I have done to the US through ShipStation. We use reference numbers for invoicing allocation purposes. Would you be able to allow/communicate reference numbers on multiple pieces from Canada to the US via UPS? Thank for any assistance.