If you have a manual transmission the problem could be the clutch petal. There is a switch on the petal that is activated when you depress the clutch turning off the cruise control, the button comes apart with age and will cause the switch not to activate. The button can be purchased from a Nissan dealer for couple of dollars. They are very easy to install, no tools are required. While you there also check the brake light button they also fail. They are the same part.
Possible clockspring failure.
Digital Control of welding when welding
What is the working principle of digital voltmeter?
It is the control box under the dash
My 89Chevrolet astro van digital speedometer stop working. How do I fix it
Most Cruise control systems will automatically deactivate if the driver applies brakes or accelerates, they do this for reasons of safety.
Electrical failure. Perhaps power is not getting from the battery to those components.
basic building block of a digital computer and it's working of each blocks
When your kidney stops working it is called kidney failure.
Electrical Failures But Engine Continues to OperateAlthough it is possible, it is not very likely because with an alternator failure, the battery will become discharged, and eventually will "kill" the ignition and thus the engine.This sounds more like a fuse or relay failure.