So to me, " wont engage" means that you release the clutch and the car doesnt move.
The clutch " wont disengage" Means that you step on the clutch but you cant get it to go into gear because the clutch didnt work.
So the first one, wont engage. The clutch is worn or the pressure plate is busted. You need to pull the transmission and get into it and replace what is bad.
The second one. Could be the fluid level is low or has air in it. Try changing the fluid and bleeding the air out of it. When under the car check the metal rod that pushes on the clutch throw arm. It should be moving in and out. Occcasionally the seal breaks and fluid runs out. If not trouble shoot the issue until it does move in and out at least 25 to 30mm.
If this is good and moving in and out OK then the throw out bearing, pressure plate or clutch inside the housing is bad. You gotta pull the transmission and look inside to fix it.
If the clutch won't engage, the clutch disc or pressure plate has probably broke apart. If the clutch won't disengage, the clutch hydraulic fluid reservoir is empty because of a leak in the system.
low freon
Most Likely Low With Freon.
the slave cylinder is bad
The clutch is wired with a hot from the battery at all times and requires a ground from the switch to engage. Check for a bad ground wire to the clutch or a bad ground connection.
Whatever the car, it has to do with the clutch. If the clutch does not dis-engage the fly wheel, you will be unable to shift or even get it into gear. Check you clutch, pedal, cable, or hydraulic system.
After you engage a gear and let out the clutch and accelerate the car wont move faster but the RPM's will move up. Also in some rare instances when a clutch disk material separates from the disk its self you wont be able to start the car or even change gears.
The clutch pedal.
The linkage or cable is broke
The A/C Compressor may not be charged with frion if the A/C Clutch does engage, or it may not engage due to fact it's not sending 12v to the electronic wiring. First start the engine and turn on the A/C, watch if the clutch on the compressor engages or not.
It depends on the type of clutch linkage. If it's mechanical linkage the clutch could be worn and the rod dropped out. If it's a hydraulic clutch, the clutch master or slave cylinder could be worn out.
check the slave cylinder,if its dry add fluid and then press the clutchin and out about 15 times