In some cases, the following error message may appear when creating UPS shipping labels:
In this case, no valid phone number was stored for the order. UPS requires a phone number for all international shipments, both from your shop and from the recipient of the shipment, i.e. the customer.
If you receive this error message, check the following settings:
Under Settings → Extensions → Shipping labels general, a shipping address must be entered.
Under Settings → Extensions → Shipping labels UPS, the option Transmit customer's phone number to UPS must be enabled. In addition, a phone number for the recipient must be entered in the dialog for creating shipping labels.