Do you know someone else with the same engine? How about installing your engine on another kart, to make sure the base engine is working. It takes less than 20 mins to swap out an engine, especially if you don’t hook up the exhaust or the chain and don’t align it. Just remove the chain cover from the other engine, and put it on yours (so use his coil), bolt it down, and plug in the stator and starter. All you want is water in the system, and then see if it cranks and starts. Shut it down right away if it starts since the water pump wont be working.
I can’t help you debug components since I don’t know enough about the system yet, but I just converted a Leopard push button engine to key start (so it can be a backup engine and plug and play into my current key start harness), and have the entire old harness, relays, powerpack, coil, stator etc for the old style engine. I was going to put it all up on ebay for sale.