Kuga power windows inoperative

Sounds like the window regulator lost its adaptation. Did you try the standard procedure to re-initialize them? Usually, it's holding the window switch down until it bottoms out, then holding it up until it fully closes, and then holding it up for a few more seconds. Does that do anything?

Yes, I've tried that procedure multiple times on all windows. No luck. The window motor doesn't even respond. Is it possible the window regulator itself is faulty, or could it still be a car electronics issue?

Possible, but unlikely all regulators failed simultaneously after a battery swap. Given your mileage, wear on the window motor or even a faulty window switch could contribute, but my gut says it's still the initialization. You've definitely performed the procedure correctly? If so, a proper scan tool might be needed to force the adaptation. Workshop time, I think.

Thanks for the insight. I took it to a workshop, and you were right; they needed a specialized scan tool to re-initialize the regulators. The final repair cost was 290€. Appreciate the help!