03 audi a4 quattro wont crank.

Could be neutral position switch but sounds like you have lost the ground to the chasy...I know that on my 4L60E In my full size truck that there is a bonding strap that grounds the tranny to the frame and also the engine and starter share the same grounding spot. When disconected the engine will not turn over....you'll get all the dash lights when you turn the key but no cranking over....hope this helps...sometimes it's the little things that you miss that kick your but. I’m not sure if it’s the same for your car but it’s a starting point