Could be a broken clutch fork, linkage, or cable depending on the setup.
You may need to adjust your clutch or replace your clutch.
Try adjusting your pedal
to start with when you push in on the clutch pedal you are disengaging it. Your description sounds like the clutch has clutched its last clutch What if it is not the clutch?
There is ( or should be ) a switch on your brake pedal lever that tells your brake lights to come on. Could this switch be incorrectly mounted on your clutch pedal instead? Do you have a switch on each pedal? If you do the one on your clutch is so the car won't start unless the clutch is depressed. It might have the wires reversed or the switches might both be mounted on the wrong pedal.
If you allowed the master/reservoir to drain empty while the line was disconnected or installed the master dry, you may have to remove the master and bench bleed it first. Always keep the reservoir full during the process.
It sounds like something is defective in the clutch pedal linkage, or actually within the clutch itself.
Clutch pedal switch or deteriated clutch pedal switch pad.
If you have to hold the clutch pedal to the floor to engage gears in a 1985 Nissan 200SX, it may indicate a problem with the clutch system. Possible issues include low hydraulic fluid levels, air in the hydraulic lines, or a worn-out clutch master/slave cylinder. Additionally, the clutch itself could be worn or damaged, leading to insufficient disengagement. It's advisable to inspect the clutch system for leaks and functionality.
if I understand the question you asked correctly, I would say you are in need of a clutch but it might need adjustment but not likely.
If it will go into gear when the engine is off but not when the engine is running, the clutch is not disengaging. It could be the clutch, possibly warped or put in wrong, or it could be the hydraulic clutch mechanism.
Dont jump them, its not a switch, its a transducer and you could wreck your pcm by jumping the wrong one. Run a power wire directly to your compressor to get the clutch to engage. If it doent engage then, it is your clutch. Remember to first check refridgerant level and fuses/relays. Good luck.
something is wrong with the clutch or something is wrong with the gas pedal. But it depends on the car. It happened the same with me with my 2009 Fararri. If its a car that will work but if its a truck than I dont know