If the time on the display counts down after you pushed the "start" button but the microwave does not make any noise - most likely the problem is a bad secondary interlock switch and/or bad wire terminals.
Usually this is a very bottom switch (#1446 on the
break down diagram).
To access this switch you have to remove the two screws holding the top grille and the grille.
Remove the screw holding the control panel. Slide the control panel up and pull the top of it toward yourself to open.
- The part number for the secondary interlock switch is
AP2024337
Here are the break down diagrams for the GE microwave
Model JVM1340AW02
Gene.