The Sims Medieval wont start

Hello,
customer service sent me here to start a thread because customer service couldn't help me in the chat.

My problem: The game doesn't start - after I clicked Start in the launcher, the launcher closes and then reopens straight away, as if the game crashed straight away. I have Windows 11 and have already tried opening the game as administrator and starting it in compatibility mode.
Both just led to the error message: "Unable to start, please reinstall the basegame". The game was so great, please release an update for the game so that it can be played for everyone again