Mangohour No Shipping Method Available

Hello! I am working on a web store that calculates shipping based on USPS postal codes and product weight. I set up the weights and shipping costs in the table rate plus plugin and I set a weight for each item in the product description. I have the plugin enabled but when I test the checkout I receive this error: “No shipping method has been selected. Please double check your address, or contact us if you need any help.” How do I ‘select’ a shipping method or make the necessary fix to complete the transaction?