We always ship USPS. Just had an order where Amazon is only offering UPS, but customer's address is a PO Box. Do we just cancel the order as bad address or how do you handle this? I’ve been selling for 10 years and never ran into this. It says the address is not available for any USPS shipping services. It’s a paperback book, 10x9x1, 12 Oz. Have shipped this same size package multiple times Media Mail.
Was the address entered as a PO Box, or was it entered as the street address of a post office with a BOX number? Amazon is known to say that the USPS doesn't deliver to post offices if it is entered in as their physical address. You can purchase the shipping label elsewhere and manually enter in the tracking number into Amazon to get around the issue.