If the solution above does not work, clear the cookies in your browser and re-login to USPS and check out. I attempted placing an order 5 times (3 with a CC, 2 with Paypal) before clearing cookies just for *.usps.com, and the order went through immediately.
If the solution above does not work, clear the cookies in your browser and re-login to USPS and check out. I attempted placing an order 5 times (3 with a CC, 2 with Paypal) before clearing cookies just for *.usps.com, and the order went through immediately.