Explain.
When ignition key is turned, the headlight turns on, vboost is heard to cycle and fuel pump may emit a few clicks?
Is engine kill switch on or off?
So when starter button is pressed, the engine turns over?
Does it try to catch? Ie you hear the engine firing infrequently. Yes sounds like it's almost gonna start until the starter clutch starts clanking and then have re-push the start button.
I guess you will have moved the choke lever up and down when turning over? Yes
Remove fake tank and top of air filter housing and try spraying carb cleaner into each of the carbs as engine turns over, if it tries to 'catch", would tend to show ignition is fine. Already Done, no change.
Can always test spark by pulling off a lead, fitting a spark plug and crank engine over. On the list to be done.