Here are some thoughts for you.
If you Cruise is vacuum operated check the vacuum connections for leaks or blockage. If it is electrically operated check all connections, including the ones on the clutch, brake, including the emergency brake, and multi-function switch. The switches mentioned turn off the cruise control if any of the mentioned items are used, e.g. the brakes.
Lastly the clockspring needs to be considered. There are three functions run through the clockspring, that is the horn, the cruise, and the air bag. If more than one of these things is not functioning then it is a good bet that the clockspring is at fault, or there is a connection problem. Connection problems can be a corroded connection, a loose connection, and/or a broken or shorted wire in the harness. The clockspring is behind the air bag and the air bag MUST be disarmed before it can be removed safely.