In order for the Starter Solenoid to engage, to roll over the engine, (A) the PTO Switch has to be in the "off" position, and (B), the Brake Pedal has to be depressed.
Now either switch could be bad, or a wire connection to either switch.
AS A TEST......
Run a Jumper Wire from the Brake Switch wire RED/BLK to the small (RED) terminal on the Starter Solenoid. Turn the Ignition Switch to start, does the engine roll over ??
