Eu4 won't start anymore after reinstalling

Make sure you verify your files.

Moved to Tech Support.  

Changing the EU4 version has no effect on whether the launcher will start. They are separate applications.

What happens if you run eu4.exe directly from File Explorer?


As to the launcher issue, Please try this:

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

Delete the following folders if still present:

- C:/users/{userName}/AppData/Local/Programs/Paradox Interactive/
- C:/users/{userName}/AppData/Local/Paradox Interactive/
- C:/users/{userName}/AppData/Roaming/Paradox Interactive/launcher-v2/
To see the AppData folder you'll need to enable View Hidden Items in File Explorer.

- exit the Steam app entirely
- run steam.exe as the Windows Admin user
- run the game from the PLAY button in Steam

IF that doesn't help, in this folder are some .log files:
C:/users/{userName}/AppData/Local/Paradox Interactive/launcher-v2/
Please attach them here.
To see the AppData folder you'll need to enable View Hidden Items in File Explorer.