Brake Lights don't work

I have a 2000 Pontiac Montana with approximately 150,000 miles. The brake lights will not work. The tail lights and the turn signals work. The brake light on the hatch works. I have replaced the brake light bulbs and the stoplight switch but it has not helped solve the problem. I bought the van used 2 1/2 years ago and the only repair work that I have had done is replacing a belt and had the starter replaced about 2 months ago. Please help!