My key stopped working to my 2008 C300. When in the ignition in any position the car did not recognize the key even being there. The batteries are working based on the small red light illuminating when I press buttons (and I replaced them). I managed to reset the key which got the car to recognize that a key is there, but now does not think it is the key for the car. Can the key be fixed, or does it have to be replaced? Thanks!