support.microsoft.com And run the x86 and x64 installers there.
IF that doesn't help, also Install ALL these Microsoft modules:
Download Microsoft Visual C++ 2010 Service Pack 1 Redistributable Package MFC Security Update from Official Microsoft Download Centerwww.microsoft.com
Download Microsoft Visual C++ 2015 Redistributable Update 3 RC from Official Microsoft Download Centerwww.microsoft.com www.microsoft.com (run dxsetup.exe after extracting from this download)
Add CK3.exe to the exceptions list of your antivirus app; ESPECIALLY if you have Windows Defender, add it to the Ransomware "Apps Allowed Through" list.
If those don't help:
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 here your Documents/Paradox Interactive/CK3/pdx_settings.txt .
From your Documents/Paradox Interactive/CK3/logs/ folder, attach here system.log , error.log