I’ve had a few random no spark issues on the multiple Vespas I’ve had.
On one of them the wire in the kill switch was pulled off of the terminal and grounding out on the handle bars.
Another had corrosion in the spark plug wire where it screws onto the coil and at the spark plug boot.
I’ve also had a engine that had a break inside the wire coming off the ignition coil not sending power to the ht coil.
I had another engine that the return spring on the points broke and was grounding itself on the points cam.
I’m not saying any of these are your issue just a few things I found in picking up non running Vespas.