over 2 years ago - AndrewT - Direct link
Have you moved your Windows User Documents folder somewhere else perhaps?

Please try this:

- exit the Steam app completely
- uninstall Paradox Launcher v2 from the Windows "Apps and features" utility, if still present.

Delete the following folders if still present:
- C:/users//AppData/Local/Programs/Paradox Interactive/
- C:/users//AppData/Local/Paradox Interactive/
- C:/users//AppData/Roaming/Paradox Interactive/launcher-v2/

- run steam.exe as the Windows Admin user
- run EU4 from the Steam PLAY button

I hope that works for you!  
over 2 years ago - AndrewT - Direct link
Have you moved your Windows User Documents folder somewhere else perhaps? The launcher can have problems if it's been moved to, say D: or whatever.  
over 2 years ago - AndrewT - Direct link
I think you'll find the launcher is in C:

Please try installing EU4 in C: also; while that should not be a problem it is worth the test I think. Do the process in post #2 above afterwards.

Good luck!  
over 2 years ago - AndrewT - Direct link
Did you do my process in post #2 above? You don't mention it either way.  
over 2 years ago - AndrewT - Direct link
There are some log files in:
C:/users//AppData/Local/Paradox Interactive/launcher-v2/

Attach them here please.  
over 2 years ago - AndrewT - Direct link
Mixed messages in that log .... download this file:
https://forumcontent.paradoxplaza.com/emailsignatures/2020.2-win-prod.zip

Extract the three files in it and place them over the three older files with the same name that are in the Steam EU4 folder, where eu4.exe is. If Windows asks you to confirm the overwrites you are in the right place.

THEN do the process in post #2 above again please.  
over 2 years ago - AndrewT - Direct link
Actually that's a completely different error than before.

I've not seen it before, but it looks like a file access issue. What antivirus do you use?  
over 2 years ago - AndrewT - Direct link
Okay, well make sure these apps are all allowed through it:

steam.exe
eu4.exe
dowser.exe
bootstrapper-v2.exe
Paradox Launcher.exe  
over 2 years ago - AndrewT - Direct link
I don't know Avast at all, I'm sorry. You may need to contact their support to determine how to allow apps through it - usually there is an Exceptions list or something like that.