Okay, I got it. So I actually had this problem before. It's because sometimes you have to pay attention to the correct order.
Here's my solution if it happens to someone else:
(feel free to create shortcuts for both launchers to the desktop)
Start the Rockstar Launcher as administrator and then the Epic Game Launcher. Then you start the game. If that works, you can start the game directly next time without the launchers first.
Why that's so, I do not know. Have a nice day to everyone who reads this 😄