Hi Serkan,
That's an error message of last resort so I'm not really sure what happened there. In general there's no reason why you cannot run both on Windows 11. I would suggest reinstalling NEMO and making sure you have the latest version (currently 2.1).
You might also want to check the Help: About screen in LEAP to see if there is any indication there of problems. In the one attached here, you can see how things look when Julia and NEMO are properly installed.
Good luck!