I found that my Windows Defender settings were disabled, saying 'managed by organization', so I followed this guide to fix it (essentially getting rid of the
HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows Defender key and subkeys.
After a reboot, Windows Defender is still unable to start the service. A look at the service dialog and this is what I see:
The same problem for the related
Windows Defender Antivirus Network Inspection Service. How do I fix this?
Edit - I found this in the event log -
The application-specific permission settings do not grant Local Launch permission for the COM Server application with CLSID
Unavailableto the user
NT AUTHORITY\SYSTEM SID (S-1-5-18)from address LocalHost (Using LRPC) running in the application container
(Unavailable). This security permission can be modified using the Component Services administrative tool.
I opened the Component services tool, but there's no mention of this component, and I don't know how to use this.