Will not go into gear while motor is running.
 

The clutch pedal on my 92 miata was loose and would not engage, so i replaced the slave cylinder, and it still would not engage. I replaced the Clutch master cylinder, bleed the clutch and changed the transmission fluid. The clutch pedal is now really stiff but will still not engage. It will go into each gear while the engine is off though. Do you think i have to replace my clutch and pressure plate or is the problem simpler than that?

More thank likely the clutch.

You can try this but make sure to dot in a safe area.

place car in gear start the car, does it move with the starter while clutch pedal depressed?

If so something else is going on.