Jet dry for dishwashers?

I filled the reservoir with Jet Dry nearly four months ago, and I went to check on it and see it if needed more, and its still full!!!! Can anyone tell me why the stuff isn't being used? Its a maytag JetClean dishwasher that came with the house we bought this fall......no paperwork was left behind on the appliance, and I don't have a serial #, etc to call the customer service line with