hi ,
Look at this post on Windows Defender and see if Anti Virus is affected similarly.
urc.exe and UE Fortnite binary get wrongly flagged as Malware from Microsoft Defender
Next you need to check that the installation is working
Verify UEFN/Fortniite
These must be “Run as Adminstrator”.
If you are using Epic Games Luncher you must start as “Run as Adminstrator”.
Check that your Project path is NOT on OneDrive, but on a local drive