After applying these fixes and getting CATIA to launch, your work isn't entirely done.
If the software closes immediately, re-check the CNEXT.exe compatibility settings. Summary of Fixes Run as Admin + Disable Antivirus [1]. Licensing Error Install DSLS manually + Apply License. CNEXT.exe crash Compatibility mode (Win 7/8) + VC++ Redist. White Screen/Graphics Update GPU Drivers / Disable Fullscreen Opts. install catia v5 r21 on windows 11 fixed