Welcome to Allpar. If none of the windows work, I would think that the problem would be at or before the Master switch. How much were they able to share with you or print on the repair order about what they did or didn't find?
Were they able to trace any of where the power began or where it ended? The TIPM (Totally Integrated Power Module-the main electrical system management module) may supply power to the switch and may have stored a fault code related to the power windows. Were they able to access any fault codes?
Were they able to rule anything out in order to reduce the number of possible causes? The power window circuit on these is fairly simple as far as modern power windows go.
Did they have electrical diagrams and since you probably paid a diagnostic fee, did they let you have any of the wiring printouts?