BUICK REGAL BRAKE LIGHT NOT WORKING

My Stop Lamps Do Not Work. The Upper Back Window One Does Though.I Changed Or Checked All Bulbs And All Taillights Work. My Blinkers Dont...

Two Brake Lights Don't Work, Center Brake Light Does, Was Told Car Has Brake Light Relay But Can't Find It.I Changed The Bulbs And Checked...

My Brake Lights Dont Work But My Tail Lights Still Do.