USPS - No Valid Shipping Options

Hello,

We are using the Markepress plugin and set up shipping through USPS. We are receiving an error "No valid shipping options found. Please check your address carefully.".

We've searched the forums and from what I've read, most people have failed to call USPS and activate the account once it was created. We instructed our client to activate their account as the instructions stated and they forwarded me the email they received (below) so it is my understanding that everything is setup correctly. I have tried 4 different addresses and it still does not work.

Email from USPS.
Congratulations on completing your testing using the U.S. Postal
Service's Web Tools Application Program Interfaces (APIs). Your
profile has been updated to allow you access to the Production Servers.

At this point - I am not sure what steps I should take to resolve.

Please advise.
Thank you in advance.
Brian