CTS Key Fob Stops Working
 

I locked my car the other day, and then realized a window was down. I unlocked it and inserted the key to start the engine and put up the window, which I did. I then removed the key and got out. When I tried to lock the car with the key fob it would not work. I thought the fob battery was bad. Upon returning home and putting a new battery in, the fob still does not work. I tried the second fob and it also does not work. It seems as though the fobs and the car have lost their link. Any idea what the problem might be or how to reset the fobs link to the car? Thanks,