In some cases, you may get the following error message when creating UPS shipping labels:
The error message "The UPS API could not process the request sent by us. Missing or invalid Shipper phone number" means that UPS could not find a valid phone number for your shipment. UPS requires a phone number for all international shipments, both from your shop and from the recipient (your customer). If you receive this error message, please make sure that:
1. A shipping address is entered under: Settings → Extensions → Shipping Labels general.
2. The option "Transmit customer's phone number to UPS" is enabled under Settings → Extensions → Shipping Labels UPS. In addition, a phone number for the recipient must be entered in the "Create shipping label" dialog.