API Disabled: Rate V3

I am using the SOAP API, FedEx v.10.2.1.124. I just added ShipRush for USPS and when I attempt to submit for a rate, I get the following:

API Disabled: RateV3. The RateV3 API is no longer available. Please follow the RateV3 to RateV4 transition guide in the announcements section at http://www.usps.com/webtools to migrate to the latest version or contact your software provider or shipping administrator for assistance. 80040B1A

What should I be looking at/for?

Thanks!