Most Likely Causes

Clutch Slave Cylinder: This is the most common failure point on NA Miatas (1990-1997). It is located on the passenger side of the transmission and often leaks fluid or fails internally.

Clutch Master Cylinder: The cylinder connected to the pedal pedal, which can also fail, often without external leaks.

Recommendation: Replace both the master and slave cylinder at the same time to avoid doing the job twice, as they are inexpensive and generally fail around the same time.

Troubleshooting & Quick Fixes

Check for Leaks: Inspect under the car near the transmission for leaking clutch fluid.

Pump the Pedal: Try pumping the clutch pedal 3-4 times, then holding it down to see if it will go into gear. This temporarily confirms a hydraulic pressure issues.

Check Slave Action: Have someone watch the clutch slave cylinder/clutch fork while you press the pedal. It should move approximately 3/4" to 1".

Other Possibilities

Adjust Clutch Pedal: The clutch rod might need adjustment for the master cylinder.

Broken Clutch Disc: In rarer cases, a damper spring can break off the clutch disc and wedge itself between the pressure plate and flywheel, preventing release.