My new Stromer OMNI ST1 (e-bike) won't start anymore. What can I do?

Has this happened to any of you? I'm currently on vacation in Ticino and went on a bike ride today and made a stop. I turned it off and sat in a café for about 10 minutes. Then I went back to the bike. I pressed the start button but nothing happened except a dark white screen. I waited 5 minutes for it to do something but nothing happened. Then I pushed it and suddenly the alarm went off (I forgot that it's set to alarm if you push it without it starting 🙁). I couldn't go a single meter. I tried taking the battery out but it didn't work unless I got into the menu to unlock the battery compartment. I then called the TCS (explanation for Germans and Austrians: this is the same as ADAC and ÖAMTC) and they came. They towed the electric car and took me to the campsite where I was on vacation. Unfortunately, they couldn't help me any further. What should I do now. I look forward to every answer!