If there's too much time between runs, fuel can evap outta those tiny tubes in the carburator and build up blockage in the idle circuit.

Mebbe open the throttle up to a more high speed area of 1/2 or 3/4 throttle and then see if it starts. If it does, then your idle circuit is blocked and a boilout of the carb, i.e., carb cleaning, would be in order.