If your engine cranks, but won't start, the problem is the seat switch. Pull up on your parking brake lever until the light comes on and I bet you it will start as long as the brake light is on. As soon as you drop the lever, it will die. That's the seat switch disconnected or faulty.
If the engine won't crank over, look for the PTO light on the dash. If it is on when the PTO is Off, your problem is fuse #2 is blown.
If the engine won't crank and the PTO light is not on, it could be the neutral sensing switch in the transmission, but most likely dirty battery terminals.