It could be that the bulb is burned out. Like half of the lights in my gauge cluster needed new bulbs when I got my Civic. It takes patience to replace them, but I love my lights so it's worth it, IMO.

You have to take the cluster out, pull the face off (carefully), take all the harnesses loose - obviously it will be easiest when you take the gauge cluster out, then pull the back off. At that point you should see all the bulbs and you can replace them with bulbs from Autozone or whatever.... theoretically. I don't know what year your car is so about all I can tell you is how my own experience went.