USPS have resolved their unexpected technical issue. USPS Shipping rates are now fully available.
Posted Dec 07, 2016 - 19:01 EST
Monitoring
USPS is experiencing an unexpected technical issue. If you've added USPS to a shipping zone, then shipping rates from USPS aren't appearing at checkout. This may mean some customers can't complete their purchases.
We recommend that you add price-based or weight-based shipping rates or rates from another carrier to shipping zones where USPS is active.
We'll post an update when USPS is back up and running.