Reverse block of Windows 10 upgrade to Windows 11

On a PC that has been blocked from upgrading to Windows 11 you will see registry keys as below with similar values within: Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\WindowsUpdate

To unblock the upgrade, you need to delete TargetReleaseVersion, leave ProductVersion as it is.

Untested: I don't think the TargetReleaseVersionInfo value matters once TargetReleaseVersion is disabled.