I just looked out my reservations and looked again online. I found that the train on 24.07.23 from Milano Centrale to Napoli Centrale no longer exists. I have it reserved from 4:10pm to 9:13pm (train number: Frecciarossa 9551), but online I can only find a train from 4:30pm to 9:03pm (train number: Frecciarossa 9647).
What can I do now that I have already paid and booked the reservation?