what model ?
probably a dry solder joint on the relay -possible
or
the physical window switch -could it be? both front switches at the same time, the rear windows still work
or
the wiring loom got pinched -can I check this myself?
or
the window motor is burnt out -possible but I never had any signs of it going.
or
the window mechanism has become dislodged, or a plastic runner/guide has failed due to fatigue or age -doubt it but I will check like I said both front at the same time