5 days ago - AndrewT - Direct link
Ah, that is usually an antivirus app getting in the way. What antivirus app do you use? You need to make sure all these apps are in its exceptions lists:

ck3.exe (in the Steam CK3-binaries folder)
dowser.exe (in the Steam CK3-launcher folder)
C:/users//AppData/Local/Programs/Paradox Interactive/launcher-v2.2023.1.1/paradox launcher.exe
C:/users//AppData/Local/Programs/Paradox Interactive/bootstrapper-v2.exe

IF that doesn't help, also set each of those .exe files (EXCEPT ck3.exe !) to run as the Windows Admin user.

Then the game should run from Steam/our launcher, and enable all the DLCs.