As mentioned, pulling the REAR brake lever firmly releases the wind up starter spring. The rear brake cable goes through an adjustable arm on top of the trans case before terminating at brake housing. If the adjustment is not right it will not work.
Has set for a few years?? Very likely rear brake drum is rusted up and not allowing you to pull brake cable far enough to release wind-up spring. You should be inspecting brakes before riding anyways.
Procedure calls for adjusting brake first then adjusting the starter arm after.