1992 Buick Roadmaster cruise control

I had the same issue with my cruise control. Is your third brake light working? I know that this sounds strange but they are connected. Check the bulb and see if it is blown. If the bulb is good, clean all the contacts that the bulb goes into. Also clean the connecters for the rear window latch. This happened to me about a year ago, once I cleaned all of this up it worked great.