Windows and roof not working with smart key
 

I have 2004 E500 and can't seem to get the smart key to operate the windows or roof. I have checked the owner's manual and held the unlock key for the 3 seconds and still nothing. I have checked everything I can think of and still can't get it to work. The windows and roof work from the inside but not the smart key. Need help, please.

The smart key must be pointed directly at the infrared receiver & hold the button.
You must be with-in 3 foot of the car while performing that task.

I have done that and still nothing. I have a friend that has one like mine and we have compared the two and mine still doesn't work.