[2020] I cannot launch any paradox interactive game.

We now have reports of this on AVG, Avast and possibly Kaspersky.

You need to make sure all these apps are in its exceptions lists:

dowser.exe (in the Steam CK3 folder)
C:/users//AppData/Local/Programs/Paradox Interactive/launcher-v2.2020.16/paradox launcher.exe
C:/users//AppData/Local/Programs/Paradox Interactive/bootstrapper-v2.exe

Good luck!  

Matt.32 said: I added these files to my avast exception list and CK3 isn't working:

C:\Program Files (x86)\Paradox Interactive\launcher\Paradox Launcher.exe
C:\Program Files (x86)\Paradox Interactive\bootstrapper\Bootstrapper.exe
C:\Program Files (x86)\Paradox Interactive\games\ck3\launcher\dowser.exe
C:\Program Files (x86)\Steam\steamapps\common\Crusader Kings III\launcher\dowser.exe

Those first three are not valid paths for this game in Steam? Do those files really exist there?

In any case the bootstrapper error is caused by Avast quarantining these files:

C:/users//AppData/Local/Programs/Paradox Interactive/launcher-v2.2020.16/paradox launcher.exe
C:/users//AppData/Local/Programs/Paradox Interactive/bootstrapper-v2.exe

You need to release them from quarantine and tell Avast to leave them alone in future.

x8ight said: I had a couple versions of the launcher that I added - the paths looked similar to what AndrewT posted: `C:/users//AppData/Local/Programs/Paradox Interactive/launcher-v2.2020.16/paradox launcher.exe ` ... also added firewall exception rules

That will do no harm, but the firewall has nothing to do with this problem, just so you know!