Piaggio Typhoon Intermittent Electric Start

Hi guys,
So I have a 2019 Piaggio Typhoon 50cc that ive been fixing up as it’s been sat in my garage for nearly 3 years. I swapped out the carb and spark plug and managed to get it starting but encountered a problem. if I leave it for about an hour and come back to it I can’t use the electric start until I start it with the kickstart and then from There the electric starts works fine. Not sure why but is really annoying as I need to sell it. Please let me know if anyone has any ideas.
Thanks

 

What's the battery voltage before you start it?