I have had this same issue all morning. My entire software infrastructure has been offline after my devices updated to Edge 121.0.2277.83 and gave me the ERR_SSL_KEY_USAGE_INCOMPATIBLE issue.
I fixed it through the following steps:
- I had to create a new self signed SSL certificate through PowerShell, using the following command: New-SelfSignedCertificate -FriendlyName ANY_CERT_NAME -DnsName YOUR_SERVER_PC_NAME -KeyUsage DigitalSignature (the main change here is the KeyUsage type - the IIS Manager wouldn't let me create self signed certificates with this type).
- Go into your IIS Manager, and edit your sites' bindings to use the newly created certificate. This guide shows exactly how I did it: https://docs.tenable.com/identity-exposure/Installation/Content/06_Manage/view-IIS-certificate.htm
Hope this helps.