Scooter won’t start with electric starter?

Hello dear users,

My Keeway RY8 simply won't start with the electric starter. I've replaced the alternator and recently the starter, and it still won't start. It starts perfectly with the kickstarter and runs well. The starter turns strongly, and everything sounds fine. It can't be the battery; I've measured it and tried a different one. What else could be wrong?

I look forward to any answer and thank you in advance!

Greetings Stefan727