Well, they do burn out with age, so either it's unplugged for some reason (doubtful), or it's burned out. Search around for how to pop out the clock pod. Basically use a plastic screwdriver and wedge it out (there are no screws holding it in, just clips), and check the connection. If you have a multimeter, also check for 12V from the power line.
If those are all good, then it's just burned out. Either find a used one in the classified, or replace it with a 3-gauge cluster if you've been looking to add some gauges.