Q:-  While cutting the plasma power source stop working because of low air pressure how to restart cutting from the point in stop cutting?

A:- Make sure that your ARC FEED BACK is set in your CNC controller. If this parameter is set one if the plasma stop working the CNC will also automatically stop movement.

In this cause you can just press PREHEAT key on the controller key pad to restart cutting and movement together.
If your plasma power source is old model and you are not using ARC feedback, then Press RED key to stop the machine movement. As the machine movement come to a paused a four options will appear.  Press BACKWARD [F6] and the machine will start moving back along the shape it was cutting. As it move back and reach the point where it stopped cutting press RED key to stop the movement. Next press PREHEAT key on the controller keypad to restart cutting operations normally.