New
#540
Not quite (but it comes close). At least we now know why windows update isn't offering to download the 2004 feature update, it's already been downloaded, installed, and just waiting for a restart (and to fail again). The log files may hold a clue...
https://support.microsoft.com/en-gb/...sion-of-window
I would try the easiest fix first and work my way up: Windows update troubleshooter, then Dism's RestoreHealth and SFC /ScanNow. Should all that fail, then reset windows update.
Reset Windows Update in Windows 10
I would expect the feature update to be offered again after a reset. If so it's up to you whether you want to risk trying it again.