Guys sells you a lemon and his customer support is to send you to MA?
What a swell guy.
I like the timing idea as well. Something may have moved if the seller was working on it and didn’t secure the points or stator plate.
I don’t know how long that 70cc Kit has been on there. If it’s new, maybe the head is a little loose? My kit blew its head gasket right away when it was new. (Not a big deal on Moped, so don’t worry).
Don’t feel bad about bugging the seller. You did nothing wrong. The decent thing would be for him to help you get the “running” moped you were sold running again.
But, you certainly are in the right place to learn to fix it yourself.