Probably has something in the kill switch/on off switch. A little sand could have gotten in there when it was sprayed with the cleaner.
I'm not sure if you are saying the spark plug is completely dry or the unit.
I would pull the black plastic control off the switch and see if you can get some electric parts cleaner in there on it.
Check all the wiring to make sure everything is plugged in good, maybe he bumped something spraying in there.
The other thing is check the oil as there is a low oil switch.
You can do all the basic diagnostics on it and check the switch, it's usually simple on these. If it's not a quick fix it will be frustrating and take a good bit of time.
Keep us posted.
If it's to much to type it all out just shoot me a PM and we can exchange #'s.
Brett
Also while I'm at it, welcome to AS since I haven't seen you around
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I've messed around with one or two if these units.