I can only operate one of three power windows

The car might have a main window switch that shut everything but the drivers side window off.

The master window switch has been changed. Already replaced it. all switches showing getting power but don't work. Going to try the ECU and reset it. also understand a battery being low or being changed can cause problems. Car will shut down accessories if the battery level is low. goes into a self preservation mode. None of these websites know that. They all say buy a new switch.

If the battery was low enough to cause the ecm to go into a self preserve mode then the guys issue would be that his car wouldn't start not an issue with just his windows. Have you tested the window mirrors or is your mechanic just assuming it's a wiring issue. Pull the interior door panel off and put power to one wire and ground to the other to see if it does anything, switch polarity if nothing happens. I saw 4 window mirrors go out on a guys car in two weeks.

Motors not mirrors and the window motor has nothing to do with the Engine Control Module

Are you certain that the other three window motors are good? Have you tried to put power 12volts directly to them to see if the work? Unplug the motor power wire from the window motor there should be three wires/pins. One wire is for the ground the other two are for up down. Get a long piece of wire hook it to your battery and use it to test the motors. I have a Dodge Durango and the center wire/pin on the connector was ground. So I put the ground wire from the battery on the center pin and then put the hot or plus wire on the top and then the bottom pin. My motor was good and it was the switch on the window that was bad. To be safe you can put a 10 amp fuse inline on the positive wire. Good luck.