Hi David, thanks for sharing those details and screenshots.
The error code 0x800f0805 usually means the update can’t be applied because Windows Update components are either corrupted or the system isn’t fully prepared for ESU updates yet.
Since Windows 10 support ended, the ESU program requires a valid ESU key and a special preparation update before cumulative patches like KB5066791 will install.
Let’s start with a few quick checks: first, confirm your ESU key is installed and activated by running slmgr /dlv in Command Prompt.
Next, try resetting Windows Update components and then run DISM /Online /Cleanup-Image /RestoreHealth followed by sfc /scannow to repair system files.
If those steps go well, download and install the ESU preparation update manually from the Microsoft Update Catalog, then retry KB5066791.
Do you know if the ESU key was already activated on this device, or should we include that step too?
Regards,
Aron