I recommend you start with an analog (not digital) multimeter.. might find a cheap little one for $10 or less.
Set it to the voltage function Hook up the voltmeter's red lead to the 'hot' wire of the kill switch. This wire goes to the points. The switch grounds the wire, grounds the ignition and kills spark..
Ground the meter's negative lead to the frame or engine block. Set the voltage range high as possible.
Start the bike and watch the meter.. it should read zero volts unless the Kill switch is activated. Then the voltage should spike.
An intermittant short to ground would make the meter's needle jump around.. This means some wire is grounding when it shouldn't.
Another possibility is the kill switch itself is bad..
Another is a loose or corroded connection anywhere in the ignition circuit.
_it ran PERFECTLY, then, I got off work and it wouldn’t start_
Could someone mess with the bike while you were at work? any missing screws or notice anything odd around the ignition key switch or anything weird anywhere on the bike?