The microwave would appear to be working - light is on, makes a noise like when it was fully operational, timer counts down but when food is removed it is stone cold

If your Emerson microwave is turning on and counting down but not actually cooking or heating the food, there could be a few potential causes for this issue. Here are some steps you can take to troubleshoot the problem:

1. Check Power Levels: Make sure the microwave's power level is set to the desired level for cooking. Some microwaves have adjustable power settings, and if it's set too low, it may appear that the microwave is running but not cooking properly.
2. Door Interlock Switches: Microwaves are equipped with safety interlock switches that prevent the microwave from operating when the door is open. If any of these switches are malfunctioning or not engaging properly, it could prevent the microwave from cooking. Ensure that the door is fully closed and the switches are working as intended.
3. Turntable and Support: If your microwave has a turntable, make sure it's properly seated on its support and able to rotate freely. If the turntable is not turning, it could result in uneven cooking or no cooking at all.
4. Magnetron Malfunction: The magnetron is the component responsible for generating microwave energy for cooking. If the magnetron is faulty or not functioning properly, the microwave may appear to operate but won't actually heat the food. A malfunctioning magnetron usually requires professional repair or replacement.
5. High Voltage Diode or Capacitor: The high voltage diode and capacitor work together to convert the high voltage output from the transformer into microwave energy. If either of these components is defective, it can prevent the microwave from cooking. Again, professional repair may be necessary.
6. Control Board or Circuitry Issues: A malfunctioning control board or other electronic components could also lead to a situation where the microwave appears to operate normally but doesn't actually cook. If you suspect control board issues, it's best to contact a professional technician.
7. User Manual: Double-check the user manual for any specific instructions or troubleshooting steps related to cooking issues. The manual may provide guidance on common problems and their solutions.

If you've checked these common issues and the microwave still isn't cooking, it's advisable to stop using it and contact Emerson customer support or a professional appliance technician for further diagnosis and repair. Microwaves contain high-voltage components that can be dangerous to work with, so it's important to prioritize safety and seek professional assistance if needed.

Sounds like on reassembly you reversed wires to door switch.
switch might have letters C NO NC (common, normally open, normally closed) one wire goes to C common, the other to NC normally closed. Try reversing the wires.
If you use meter measuring continuity meter on C and NO should be high resistance until you press switch.
meter C to NC measures low resistance until you press switch then measures high or infinity (open)

You didn't tell us what you were doing when you had trouble, so it's hard to say. Many microwaves will appear to work normally (timer counts down, light comes on, etc.), but they will not come on if the door isn't completely closed. Usually they have a fan that runs while the microwave is cooking, and this won't come on. If the fan is on, but the food isn't getting hot, there's a good chance your microwave is dead. You can try to call a repair service, if it's in warranty, but the cost of repair is often close to the cost of a new unit with microwaves.

The problem is one of the door switches has failed, usually caused by food partical buildup, switch must be replaced for normal operation.

The part of the oven called the "magnetron" (this part is what creates/generates the microwave energy that heats the food or liquid) is burned out, the cost to repair is more this part is more than the cost to replace with the cost of Microwaves so depressed by the stagnant economy.

The door switches are slightly out of alignment. If you run the microwave and shift the door up or down, the micro might begin working..
The control panel must be removed and the door switches adjusted. I would not suggest you doing this yourself, as it may affect the microwave leakage through the door gap.

HI. in most cases, this will lead to a failed Heating device(magnetron tube).It would be wise to check the Magnetron cutoff fuse to be sure of its integrity. if the fuse is blown, simply replace it. if the fuse continues to show continuity, replace the magnetron.

(((The fuse is located inside the unit along side of the blower housing, or magnetron tube assembly)))

If everything appears to be working normally, as you say the timer counts down, the light comes on, turntable rotates etc. then the problem will be linked to the magnetron not operating & not heating the food. This could be just a thermal fuse device which may have gone faulty but if it is a magnetron fault then the cost of getting this replaced can be expensive & it might be more economical to buy a new microwave. I would advise taking it to a local repair centre, one which gives free estimates to get a quote on a price.

check or replace magnetron

You have a blown actuator. This is the device that creates the microwaves that cook the food. The cost of one of these will be as much as a new unit.