I always had problems with kill switches on riding mowers. There was one under the seat that shut the mower off if you got off while it was running. Check that. Make sure the blade is not engaged,up or down etc....
“kill switches on riding mowers”
You reminded me about the riding mower. There may be a safety interlock. Like a car where you have to have your foot on the brake or push a button by the steering wheel, you may have to be sitting in the seat for it to start.
Series.
I disconnected the blade brake on my mower. The CPSC sue me.