98 Blazer high mtd stop light inoperative

Only the high mounted stop light is out; the two side stop lights work ok. Any suggestions?

Pull the light and make sure it works by applying 12V to it manually. Another way to is to pull the light, and probe the connector and make sure when your applying the brake pedal its recieving 12volts. If its getting power at the plug, then the light itself needs to be replaced. If its not getting power to the back, check the switch at the brake pedal and make sure its working, keep tracing the circuit back until you find it.
Good Luck!