What would cause all of the power windows to not work.

@firehouse66, John, You should perhaps replace the Power Windows/ Sunroof (Circuit Breaker) as it may be faulty, see pic. below for location. Still no go, replacement master control assembly still could be faulty or not plugged securely, recheck connections/test switch. Still no go, time to remove the door panel and test the power and ground to the window motor. No power to motor there could be a break in the wire harness between door jamb and door frame(quite common), peel back wrapping/harness sleeve and inspect for pinched/broken wires. All looks good there, then remove driver side kick panel as I believe there is a pwr. window harness plug there that may be corroded and in need of a good cleaning. If you do have power to the motor, then the window motor is faulty, I know what you are thinking all pwr. window motors faulty(it could happen), but unusual, do check for power at motor plug and clean if corroded and retry before replacing pwr/w motor. Links below may help in trouble shooting/testing/door panel removal to access wiring/plugs/motor, etc.. Good luck. I hope this helped you out, if so let me know by pressing the helpful button.

http://www.agcoauto.com/content/news/p2_...

https://www.youtube.com/watch?v=0Le7cKCh...

http://ricksfreeautorepairadvice.com/tes...

http://www.justanswer.com/pontiac/2kc28-...