So I'm not sure if this will be helpful information, but I've been encountering this same problem, and I tried going into the WindowsApps directory and navigating to ParadoxInteractive.ProjectTitus_126.96.36.199_x64__zfnrdv2de78ny\launcher\bin and setting cpatch to 'run as administrator' in the compatibility tab. (Right click cpatch.exe, choose properties, switch to compatibility tab.)
When I try to run after that, I get this exception:
View attachment 708818
But after I hit OK the launcher comes up!
Um, this works.
Yeah this works, so something is going on with cpatch not having necessary permissions to read/write to the disk.
All the jazz about anti-virus stuff and such doesn't do anything.
So to do this, here are the steps:
Go to your Windows Apps folder (typically located in C:\Program Files\WindowsApps)
If it asks for permission to access, you'll need to right click the folder, go to the security tab, click "Advanced", then change the PRINCIPAL at the top (put in your windows username)
Apply, then close the window.
If it didn't ask you or you have set up access from the steps above, go to ParadoxInteractive.ProjectTitus_188.8.131.52_x64__zfnrdv2de78ny within the Windows Apps folder.
Then go to launcher ---> bin
When you see cpatch.exe, right click it then go to Properties
Then once that's open, go to Compatibility
Check "Run this program as an administrator" then click Apply.
Then try launching Crusader Kings 3.
The error that taconium got will appear, just click ok.
Play as normal.