In general it could be a number of things but here are some general tips that may help you.
1) Kickstand - some scooters have a switch that prevents the scooter from starting if the kickstand is down
2) Battery - sometimes a bad battery connection will temporarily power on the lights and the dash, but when you go to start the engine, the draw is too much and it seems like everything just dies. You may just hear a "click" and nothing else.
3) It could be a connection issue with either of your brake switches that would normally allow the start procedure. One way to check this, though I can't fully recommend it, is to bypass the ignition switch (assuming it's not the battery), and cross the terminals on the starter solenoid to see if it turns over/cranks or even starts up.
I'm sure many other on the forum can chime in as well, but often, the most elegant solution is the simplest.