Get 3 spare bulbs with sockets and temporarily wire one to each side of the clutch pedal switch and one to the starter solenoid. When it won't start look at the bulbs to see which have power and which do not. Tests aren't overly easy to do; but, they are the only option other than replacing parts through educated guesses.

Good luck!!!

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer