Yes I had the same problem with piaggio zip 50 ten days ago. It has been off the road for several months. I was not able to drain off some old petrol in the tank .. which can loose "light ends" and be less effective at vaporising and starting. I topped up the tank with fresh petrol, checked there was oil in the separate tank. OK?
Then I held down the starter button for ages say 3 or 4 minutes, when the engine then coughed. Then 12 kicks on the starter pedal. Then back on the starter button, and eventually the engine came slowly to life, very slowly . . conked out . . and maybe I did that another five times . . . but do not accelerate because the engine did not respond properly. After some more minutes everything got better. Then I let the scooter sit on its stand for another 45 minutes with the motor ticking over. And no problems at all after that . . . first push on the button and the engine just fires as normal.
I do have a proper battery charger in case the battery gets drained too much.
Good luck ... just stay determined and the engine should submit. Don't give up.
Neil
September 2009