I had the same problem. i didn't start the bike for 3 weeks (the bike has 15 months) and probably the battery is very weak.
After some "button push" the battery has gone dead dead.
I borrowed from a friend an electric
BOOSTER CABLE. Connected the cable from my car to the GZ battery (maintaining the same polarity "+" to "+" RED, "-" to "-" or to the engine block BLACK).
I must say: double check the voltage of the car battery and the voltage of the bike, we must have the same nominal voltage. Generally for cars is 12V. The GZ has also 12V.
After few tries, the bike has started (probably not enough gas in the carburetor).
This can be a alternative solution for starting the bike, if you have a car near you.