Check fuel levels on the tractor control panel. If fuel is present, it may be contaminated with water that has entered into the fuel tank, or the fuel may have degraded from months of inactivity.
Disengage the power takeoff (PTO) lever. Engage the parking brake as well. Restart the engine. The engine will not start unless these two actions are performed.
Inspect the electrical connections for corrosion. Inspect the spark plug connections as well. Ensure everything is connected properly. If the spark plugs look burnt or it has been more than two years since they were installed, it may be time to install new plugs.
Find the fuel line beneath the tractor. Check the fuel hose for cracks or crimps in the line. These would block fuel flow to the engine. Place the choke control into the "Choke" position and try starting the engine.
Clean the front of the tractor near the radiator. Wipe it clean of dirt and debris that can block airflow to the radiator. This can lead to engine overheating or failure.