.... pull the clutch and
see if that makes any difference.
This part is a key component in identifying where the fault lies:
The 'start enable' (which is the INPUT to the Start Switch) has two possible sources;
EITHER the Transmission is in Neutral OR you have the clutch pulled.
So ....
Pulling clutch makes no difference - problem would be in the start switch itself, oxidation/pitting of the contacts
Pulling Clutch DOES make a difference - problem would be in the Lunch Box