c240, 2003 does not open, key does not work

Hi I have a mercedes c 240,2003, that my electronic key does not open the car..I already changed the batteries in the electronic key and my e-key has never gotten wet..
What could be the problem, and what can i do to the open the car. If any body knows please tell me. i would appreaciately greaty..
:banghead: :runaround: :disappoin