Ok. Here’s what I did.
fitted lanyard switch. No problem. Wouldn’t start.
looked for a while and what I had inadvertently done was, upon tightening the cdi to ground wire. (Black/white) pulled a pin out the cdi socket.
took a while to diagnose and well worth a look in case it happened to you.
to fix, I pulled out pin. Gently crimped then inserted using a fair sized paper clip wire.
good luck