Check the wiring harness for the door where it leaves the door and goes to the door jamb (near the hinge). Unplug it and look for corrosion. It is the common point if nothing electrical is responding. It is near the footwell, and so might be what the dealer was referring to.

__________________
2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue