There are 4 thermostats (aka TCO = Thermal Cut Out) in the GE JVM1440BH04
The schematic is under the cover in a black envelope to the top left of the unit if you face the door.
Check the fuse first. You can remove the front grate, then the numpad on the right. The fuse is right behind it. It's a 250V 20A Class F fuse.
There are fo...