Shipping rates can be one of the more troublesome areas of the store, and is probably the area most commonly modified. There are a probably a hundred different variations on how to offer shipping so don’t be surprised if you find you need to do a little custom coding here to get exactly what you want! Here are some tips to keep in mind.
Most of the automated shipping rates (as well as some payment processors) make use of the CFHTTP tag in ColdFusion. This tag may not work properly on some older ColdFusion servers, or over a proxy server. In some cases you may need to have your ISP update the server certificates for a particular API if it isn’t working. Be sure to establish that this is not the issue if you are having any problems.
There are lots of other things that can also cause your store to have problems returning shipping rates. First, make sure you have correctly set your Home Country and that you did not delete the rate for the home country in the country rates (normally set to 0). Make sure you have at least one shipping method turned on, and that it is one that will be returned (domestic shipping rate versus international rate). Be sure that the products being ordered all have weights entered and shipping turned on. And when using UPS, FedEx, USPS or Intershipper, make sure the sites are up and functioning and that you have entered the correct account information. If you are using drop-shippers, be sure they all have valid addresses entered.
The UPS, FedEx, USPS and Intershipper tags can be configured to send debug information or log their transactions. This will show the actual message being returned by the servers and can be very useful in debugging issues.