Make sure you have valid weights assigned to all your products as shown below.
Another thing is to make sure you have the shipping origin settings set correctly to the location you are shipping from.
If you still are getting the error message, make sure you have valid 'real time methods' setup for the address you are shipping to.
Also, make sure you have not mistyped any of your usernames, urls, or passwords in the 'real-time shipping configurations' as shown below.
If all is still correct and you are unable to get rates ensure that the server can communicate with the shipping gateways, have your host check on this.
