The window switchpacks do unfortunately have a tendancy to just fail.
If EVERYTHING stops working, then the fault is usually some of the tiny vias (through PCB connections - the little holes). They are usually plated with copper to connect the circuit through the board, but if there's been moisture etc and they corrode out, then the circuit breaks and it stops working.
Most of the window switchpacks I've repaired, which have just stopped working have had anywhere between 1 and 5 or 6 of these connections broken. The reason the switchpack just stops completely is the ones that fail are usually ones on one of the serial bus lines - so if any of them stop, the whole thing stops.
If you are OK at some tiny soldering, then they are repairable - I used to use a 0.3-0.5mm drill bit in a small rotary tool to drill out the corrosion through the via, and then scrape a bit of the masking off the track, and solder a bit of thin copper wire through the hole to re-make the connection.
Pretty easy fix (but I do have an electronics background) but can be a bit fiddly to find where the break(s) are. I did at one point draw out the circuit diagram for most of the serial lines on the switch packs so I could just probe a number of places to check the common culprits, but I haven't found them yet in all my stuff I sent over when I moved :(