Just a quick additional bit of info.
The PC with the problem has been updated to Win 11, and the same KB4023057 update was offered on it.
That KB update worked as normal, and Windows Update works...

This particular PC with the problem is now at Win 11 and that has circumvented the need for KB4023057, although I still find it interesting that nobody knows why it is available for other versions...

Thanks Denis for the reminder of access to Control Panel via Menu, I usually type 'control' in the search box and pick the 'Control Panel'.

- - - Updated - - - 22/10/21 16:56 UK Time

WELL WELL...

Thanks Ghot - I used the 'WhyNotWin11' early July and my PC is definitely suitable to run it.
Note that there have been several versions of "WhyNotWin11" since 2.0.3.1.
Also the official Microsoft...

Nice little batch with a couple of things I've not included before - problem is the 'Cryptographic service failed to stop'.
From memory I think I solved this by using safe mode.
Anyway best way...

Thank you - will give the 'Reset ' a go and come back.
Just so you know all the information, the problem I have struggled with for several months gives the error 0x80070057 and PLEASE NOBODY send me...

.... oh and I keep getting prompts for it to be loaded via windows updates which fail.
(Sorry - not used to using the 'tenforums' system)

- - - Updated - - -

Thank you Ghot for replying -...

I have checked both in normal windows stuff and programs in control panel.
Surely the latest version dated "2021-09" is different to the previous versions, otherwise why bother.
Thanks for replying...

Hi
very simple question.
Why is KB4023057 not available for my PC in the Microsoft Update Catalogue?
This is "2021-09 Update for Windows 10 Version 21H1 for x64-based Systems (KB4023057)".
To my...

From 3rd August 2015, in reply to lolcocks on Page 6 of posts.

Are you still looking into it?
I have something similar and am wondering why this has occurred.
Thanks.