Hi, I had a mower, power-torque that failed to start because water and grease worked its way into the cut off switch area during a rainstorm driving home in an uncovered trailer; I also destroyed the fiber air-cleaner.
The rubber replacement parts are freely available; there are so many of these mowers around still. These are hard mowers to tune. It maybe worth removing the engine and coil pickup to check for rust between the coil and permanent magnet on the flywheel and sand the iron oxide material material away to give a higher current in the magneto system; then reset the gap with a business card; however if you have not dismantled this machine before, please check online for advice.
I prefer to earth the spark plug on the exhaust system, away from fuel source and on iron contacts; this is general advice for young players. There is a rubber boot that causes grease and water bound leaks into the cut-off switch when it is split or worn. You should also replace the small round rubber round piece that is lodged in the plastic body of the carburetor, which is a guide for the cut off switch. The spark from the plug should be blue; test in shade; if you are in a hurry you might make many mistakes in troubleshooting this 2 stroke machine.
If you remove the muffler you can check for problems: check for scoring on the piston/ring, cylinder assembly: dust, bad fuel/old fuel; poor lubrication; compression failure; and vacuum failure. You examine this through the exhaust port; the bore is often scored on this model, through piston and ring seizure; often from a too lean fuel mix and over-reving due to a vacuum leak.
Again this mower can be frustrating, a new ignition module is an expensive option, I would want to have a better idea of the condition of the engine before replacing the electronic module. You may be able to pick up a second hand machine in the trash with a good module. Good luck.

Gomower.