In the game launcher please set Display mode to Borderless.
IF that doesn't help, Install ALL these Microsoft modules:
www.microsoft.com
www.microsoft.com
www.microsoft.com
THEN go here:
This article lists the download links for the latest versions of Visual C++ Redistributable packages.
support.microsoft.com
And run the x86 and x64 installers there.
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.
Also if you have installed RivaTuner, RadeonPro, or a gaming VPN app called Evolve, or the MSI Gaming App, or Duet, disable it as it clashes with this game.
IF NEITHER OF THOSE HELP:
DXDIAG is a program you run from a command prompt or the Windows start menu 'run' dialog box (or 'search programs' in Windows 7 or later). 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/EU4/settings.txt and pdx_settings.txt .
From your Documents/Paradox/EU4/logs/ folder, attach system.log , error.log .