Magento Shipping: USPS “API Authorization failure. RateV4 is not a valid API name for this protocol.”

The Problem

This was a doozy today. I signed up for USPS Web Tools, plugged my User ID and test server details into my Magento Development site, and was rudely greeted with the error:

API Authorization failure. RateV4 is not a valid API name for this protocol

My initial symptom: I didn’t see any USPS rates in my front end. Enabling debugging allowed my to see the error in /var/log/shipping_usps.log.

The Fix

The problem is that the USPS test servers didn’t support RateV4. So, you email USPS support to enable production server access for your USPS User ID. And we’re all set!

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