Windows update now says not Windows 11 compatible

This page should help. Also check your BIOS to make sure Secure Boot and TPM are enabled, though I have no idea why it would be off now unless and update was to blame.

So how do actually check in the BIOS if TPM is enabled. I've been in the BIOS (F12 on boot) but can't find anything that specifically says enable TPM.

Thank you JOcean. None of those suggestions worked. PC Health Check is OK so  Secure Boot and TPM must be OK and the odd thing is that it has been OK for months - just suddenly changed

In the BIOS should be a setting for Intel PTT and that should be enabled. This web page has a good explanation of PTT.

Excellent, thank you, yes I PTT is enabled. So there is more reason for Windows update to suddenly think it is not Win 11 comparative- bizarre 

There are only certain things that might have changed to cause your situation.  Check the Device Manager under Security Devices and see if the TPM is version 2.0

Have you had a recent Bios update that might have changed some default settings, like CSM?

Have you gotten the Windows maintenance update, KB4023057, which may be responsible?

Otherwise, have you made any other changes to your system, such as devices or software?

It could just be a glitch.

The CSM or Compatibility Support Module settings are normally in with the Secure Boot settings.  But since each Bios is different, I cannot tell you where it is.  It may mention something like legacy OPRom or some other term but it should be disabled in Win 11.

The update is for checking your system for such things as free space on the drive.  You can look for the info for that update to see what all it might be doing.

Thank you TPM is Version 2.0.

Yes, KB4023057 was installed last week

Yes there was a BIOS update last week.

Sorry, you've lost me on CSM - can't find it in BIOS. Where can I find it and what should it be set to?

Thank you