Your device is missing important security and quality fixes

You are actually out of date in that my build is now 19045.3448 (and I chose not to be offered preview builds), so the message appears to be correct on that basis.

Please post a screenshot of your Update History.

Presumably the tutorial to which you refer is this:
How to Specify Target Feature Update Version in Windows 10
I have used that, and see no such message.

Thank you for your reply.

1. Type
Update History
in the search box
or search Settings for that.

2. See the huge searchable Tutorials section. (Or use e.g. Google to find out how to create a screenshot).
Take Screenshot in Windows 10
Take a Screen Snip with Snip and Sketch in Windows 10
How to Upload and Post Screenshots and Files at Ten Forums

What exactly happens if you check for updates manually?

Good, no failed updates.

petermik said:

Some time ago I used the tutorial on here to stop MS upgrades to Win 11 and stay in version 21H2
Windows update is telling me " your not up to date as your device is missing important security and quality fixes"

Version 21H2 went out of support in June.
So the message is correct.
That KB4023057 update is a bit of a red herring. It gets re-issued once or twice a year and was re-issued in August after 21H2 updates should have ended.

You'll need to update to Version 22H2 to continue getting updates.
Alter that Target Version thing to 22H2.
One method of updating to 22H2 is to run a Repair install [aka In-place upgrade] using a 22H2 ISO file.
Download Windows 10 ISO File -TenForumsTutorials
Repair Install - TenForumsTutorials - your installed applications & your own files should not be affected but it would be well worth making a new system image beforehand.


Denis

petermik said:

Did this and still no joy........

As expected.
Windows knows you are using the unsupported Version 21H2.


Denis

As Try3 says, as your chosen feature update is 21H2, you need to amend that. (Missed that possibility!)

Once you've done that Windows Update should work as normal