MarketPress shipping

MarketPress - Hi we have MarketPress running on our WordPress site. We are in Live mode with MarketPress and in testing mode with Authorize.net. We have just updated our shipping amounts and would like to test them with a product. We have our shipping set to USPS. When I enter in my address for testing - it says "No valid shipping options found. Please check your address carefully" I have entered in my correct address and I know USPS can deliver to my house - where do I go from here? It doesn't seem to let me by this message or help me to correct it.
Thanks much.