Let me see if I understand this right.
1. With the engine running, you press the clutch pedal down.
2. You move the gear shift into any gear and you can feel it go into gear.
3. You release the clutch pedal and nothing happens.
4. The engine continues to run, but the car does not move.
What happens if you press the throttle pedal with the clutch pedal out and the transmission in gear?
Have you tried putting in any other gear or just reverse?