Neutral switch for Morini 3 1/2

[Michael S]

My Morini 3 1/2 (1980) has suddenly lost the ability show neutral and hence will not start.
The gear box still selects as it should.
Nothing wrong with any other electrics or the bulb.
I cannot find the switch!
Can anyone point me in the right direction please?
Regards
Michael

[MickeyMoto]

Behind the generator cover, at the rear near the gearbox sprocket.