We've seen several reports about this and found that the most common causes are as follows:
- Avast! anti virus program
Please add ck3.exe (or the whole CKIII folder) to the approved apps list (guide: https://support.avast.com/en-ww/article/Antivirus-scan-exclusions) - Windows Ransomware
This is an odd one but it seems CKIII get stuck there now and then! Please follow the below instructions to make sure it's approved: https://www.windowscentral.com/how-allow-blocked-apps-ransomware-protection-windows-10-october-2018-update - Windows Defender
Add an exclusion for CKIII using this guide: https://support.microsoft.com/en-au/help/4028485/windows-10-add-an-exclusion-to-windows-security