Clutch won't release

1991 Prizm (aka, Corolla) dead clutch (aka SLIPS)
does engine crank and start in gear? in gear?
the first thing to check is the clutch pedal actuation system.
cable on some , and Hydraulic on othere
open hood, see that MC for clutch, is the Reservoir dry?
yes, no?
yes, then the slave or mc is bad or both, the one leaking is bad.
Most cases Hydra clutches can not cause slip. (rare)
its a cable, can if cable frays inside or rust, (big time common)
well all cable clutches need service, if not it fails.
called setting free play in the book, FSM book
I love the above post where he guesses then sets a price.
first is diagnosis prices last and varies all over planet earth
and is useless here. prices. always.
Ill look in Michell's for you.
it's not a cable system,
Mitchells shows, hydra. clutch
so unbolt the slave.(on bell)
start car in gear, does car move. yes /no?
yes, clutch ok , and slave is siezed.
no, then clutch is bad (inside bell housing) $$$$$

i posted both ways, as these era cars run to clutch systems.
that could even change mid year, production.

S= slave
Bell = bell housing
L = clutch lever.
see the 2 bolts?
some Slaves can seize (due to running old fluid full of water)
Dot3 fluid is hydrascopic and needs service every 2 years. min.
we check the MC and all parts related here.
to see if the L lever is stuck to the right above.
never condemn any clutch until these checks are done
or go broke fast. IMO

have you checked the micro switch under the seat

Time for a new clutch assuming you let all the adjustment out.

This normally means your clutch is worn down and needs replacement. Much less likely is that the clutch pedal travel needs adjustment.

Replacement of the clutch requires removal of the gearbox and is much easier with a shop hoist. I'd recommend replacing the pressure plate assembly as well.

Start with inspecting the clutch handle for any obstructions or rust.
Lubricate the clutch cable at the handle.
Follow the cable down and look for and pinching or damage.If you can follow the end of the cable to the actuall clutch mecaniism, inspect the area for clearance.
If you can disconnect the cable from the clutch mecanisim and test the clutch handle to see if the cable moves freely.
Manually try to engange an clucth with the engine off.
If it won't move, time to diassemble the clutch.

Try tighten cable adjusters, check cable for damage, check the clutch release arm for damage, if thats ok its worn clutch plates replace the clutch plates and check components for damage,

Synthetic oil is bad for motorcycles. It makes the clutch slip. After changing back to regular oil I would start it, drop it in gear, release the clutch and just wait and see if its able to "wear" off the bad part of the clutch disks. This might take a short bit and be ready for it to suddenly grab and go. If not you might have to have the clutch disks replaced.

if its a direct drive , make sure the brake is releasing for starters, If the spin basket has difficulty getting up to speed, you have a slipping clutch. You can determine this by slightly holding the spin basket when you select spin.A rapid spin up to speed shows a "good" clutch. other things to check for are a broken coupler, or any item trapped between the drum and housing, ( which is what happens most the time, )

Adding Stop slip to a manual transmission with not keep your clutch from slipping. Replace or adjust the clutch.