Modern Vespa

I took my vespa out for a ride and whilst I was driving the engine just died. I out the bike by the side of the road.
I tried to start it and it cranked when I press the left brake handle but when I turn up the gas it does not start and stops cranking.
Then the tow truck came and we took the.bike home, and the driver was about to take the bike down from the truck, the driver tried to start it and it worked, not once but three times.
What do.you think the problem was?

On modern automatic Vespas, the throttle grip must not be opened for the starting process!

Do you hear the whirring of the fuel pump before the unsuccessful starting attempts when you switch on the ignition? If not, thermal problem with the fuel pump.

Thanks. I went to check this. Yes, there is that whirring sound and the bike does start without turning the throttle too. I want to see what could have been the cause of it dieing whilst driving because I don't want this to happen again.
Any ideas ?
I checked the brake lights they both work, the spark plug is securely in place.

The brake light, or more precisely the brake light switch, is only important for starting.

If you hear the whirring of the fuel pump and the Vespa starts, this is normal. What is important is whether the fuel pump was heard beforehand in the cases in which it does NOT start.

From a certain opening angle of the throttle, the starting process is interrupted, which is also normal. Therefore, NEVER open the throttle when starting a newer automatic Vespa.