Payments are being rejected

I've been trying all morning to send some packages on USPS.com and I keep getting error messages saying my payment has been declined or that I cannot pay at this time.  I've used 2 different cards and still no way to make this work.  So super frustrating and then add to the fact that this forces me to have to go to the ridiculously understaffed post office so thanks a lot USPS.com