The clutch disc could be stuck to the pressure plate. Take off the lower pan and have someone push in the clutch pedal. With it not running try to insert a putty knife between the clutch and pressure plate and/or flywheel. You may need to turn the engine over to try several points. There are a couple of other methods that are kind of risky - one is to put it in gear and start the vehicle - it will take off so you need lots of room to experiment so you don't hit something. The other is to put it in gear and push start the vehicle which could also break it loose.
Fred
