4 months ago - AndrewT - Direct link
This has helped at least one affected user. Please do a full **clean** re-install:

- move any valued save games elsewhere
- "uninstall" in Steam-EU4
- manually delete both the Steam/SteamApps/common/EU4 AND Documents/Paradox Interactive/EU4 folders
- re-install game in Steam, run a Steam Verify when done.
- add EU4.exe to the exceptions list of your antivirus app; ESPECIALLY if you have Windows Defender, add it to the Ransomware "Apps Allowed Through" list.
- start the game with no mods active and test

In particular make sure there are no files or folders left under either the Steam EU4 or Documents EU4 locations, before installing again.  
4 months ago - AndrewT - Direct link
DXDIAG is a program you run from the Windows search box on the task bar. After running it will open a window and start collecting info with a progress bar in the lower-left corner. When it completes click the 'save all information' button and save it to a file then attach that file here.

Please attach your Documents/Paradox Interactive/EU4/settings.txt and pdx_settings.txt .
From your Documents/Paradox Interactive/EU4/logs/ folder, attach system.log , error.log .