Engine works but press the gas and nothing happens.
Is your transmission fluid at the right level? Is the color good?
Have you maintained the transmission according to your maintenance schedule?
What–exactly–does that mean?
Do you mean that pressing the gas doesn’t cause the engine to increase its speed?
Do you mean that you can hear the engine “revving”, but that the car doesn’t move?
If it is the latter case, then you should focus on lion9car’s comments regarding the transmission.