Modern Vespa

Hi, I have a 2022 300 GTS vespa. Every winter, I store the Vespa.
I take the battery out, fill the gas thank, put some additive in the gas, and store it in a non heated garage.
This spring, when I pull the Vespa back from the storage, I had a very difficult time to get it started. I had to restart the engine several time before I got it going. And the problem has persisted since. I often have to restart several time before I finally get the engine to run.
Had the battery tested twice and been told it is as good as a new.
Took the vespa to a dealer who found nothing wrong.
Never had this issue the two first year.
Somebody has an idea?

I would pull the fuel injector and look at the spray pattern. Might be clogged.

here's a scooterwest video

https://youtu.be/F_xDtly6KxU?si=WdIdKHmq2ZqoE90A

Thank you very much for your reply. Looked at the scooter west video and it adresses exactly what seems to be the problem with starting the Vespa after a few months of storage.
I will contact a dealer to get the injector cleaned up since I'm not comfortable to do it myself.
Again, thank you very much.

Fuel injectors are relatively inexpensive and easy to replace. DIY and less than 30 min back in business as will be costly to have dealer do it