July, 2020- same problem. After trying two credit cards, Paypal (through credit card), and Paypal (using balance), I called USPS customer support. Estimated wait time "over 1 hour". Tried https://www.paypal.com/shiplabel/create/. Same USPS Small Flat Rate Box, same priority, about a buck less. Click, print, zoom- took about 3 minutes. IMHO, don't even bother with USPS.
July, 2020- same problem. After trying two credit cards, Paypal (through credit card), and Paypal (using balance), I called USPS customer support. Estimated wait time "over 1 hour". Tried https://www.paypal.com/shiplabel/create/. Same USPS Small Flat Rate Box, same priority, about a buck less. Click, print, zoom- took about 3 minutes. IMHO, don't even bother with USPS.