From what you have said is sounds very much like a safety switch issue and these are a PIA to find.
There are 2 distinct circuits.
One stops the engine cranking by breaking the power supply ( & / or ground ) to the control wires on the solenoid and this is a daisy chain circuit.
The other grounds the magneto to kill the engine should you fall off and involves a lot of switches in various combinations in parallel.
As your mower will neither crank nor fire and this happens after a "bump" immediate suspect is the brake switch as this is in both the no crank and no fire circuits.
Naturally the fuse is also in both so start with them.
With the brake on the brake switch will have 1 pair of contacts closed , that is the start circuit and the other will be open, that is the kill circuit.
In the off position the switching is reversed.
As a TEST ONLY you can try bridging the contacts but be careful because if you send 12V down a kill wire to the magneto it will do exactly that and maggys are not cheap.
The PTO switch is also common to both circuits as is the ignition switch but try the obvious & easy first.
Lunch is over & I have to go pick up some parts so if no one else chimes in I will try to pull down a circuit diagram tonight ( Australian time )
