Duodeluxe, it's rather not seat switch.
Truck Doctor should work anyway.

Of course I presume, that Controlelectric knew, that the Truck Doctor should be connected to three different sockets on the truck: for indicator unit, traction and lift. All of them are visibly marked.
If yes, and there no connection to the controllers...
well I never encountered the situation that both controllers died, unless somebody burned the truck (ro example changing the polarisation of battery plug).

Perhaps the issue is simple.
Controlelectric, are you sure, all the fuses are OK?
For me it looks like some may be burned.