Remove the blower housing, and unplug the wire going to the ignition module. Crank engine and see if you have spark. If no spark, replace the module. If you have spark with the wire unplugged then check the clutch switch, located either under the frame next to the rod for the brake, or just inside the dash housing between the steering rod and the engine on the left side on top of frame. The pto switch which is located most likely under the transmission tunnel between your legs if sitting on seat, if not electric clutch. I think you know where the seat switch is located.
The PTO and clutch switch most likely prevent cranking in the first place, but have seen stranger things. If iswitches check out then you will have to look for bare wires, or shorts in the kill circuit. Mice have a tendency to chew the insulation off of the kill wire under the blower housing causing shorting of the kill wire to the sheet metal.
I hope this helps.