The first thing to check is that you have a translation service enabled and that you have entered the service code in KMFasTrans.
At the moment KMFasTrans supports a single translation service that is the Microsoft's Bing Translator. To use this service you have to register for the service and configure KMFasTrans options to use the service. Please visit: Enabling Machine Translation Service.
If in spite of the above you still have problems, please send us a Support Request.