Based upon my experience, the autopetcock is not opening, carb is not getting fuel. These are very good scooters, but have a few issues and the autopetcock is one IMO. Mine are always hard to start, if sits for any length of time. If ridden daily, will start easily the next morning, if I let it sit for a week or longer it will be hard to start.
Try manually choking the carb air intake 100%. I run after market pod airfilters, so I will wrap the air filter with a plastic grocery bag and try to start it. The extra vacuum will open the autopetcock and deliver fuel to the carb and engine will start. If you are running the OEM airbox, there is square intake hole at the bottom of the airbox, block it off to choke it. Good luck, Cheers