So you have power in the main loom?
And you have power in the door look?
And you have power in the door loom to the switch yes?
But nothing from the switch onwards?
Correct so far?
If you have tried several other confirmed working in another car switches I would then have that second car there as well to check where the power goes from the switch back into the door loom back down through the car again

It should just be a break in the main wiring which you should be able to rectify fairly easily as its all contained in the door itself

If its the main loom you can just replace individual wires but my first port of call would be to strip all the door loom out and then connect it outside the door to make checking the wires and plugs easier

You should also do a continuity check on the wires from end to end as it could be just a dry joint in the door loom

It's easy working in sierras

There should only be 5 wires in the main power loom so check that first