Hello @Terence Lo
You can try to reset the Windows update component and search for Windows Update in the Settings.
How to: Reset Windows update components in Windows
https://answers.microsoft.com/en-us/windows/forum/all/how-toreset-windows-update-components-in-windows/14b86efd-1420-***************5b1e8a3
If this doesn't fetch the update you can always try the in-place update to update to the latest version of windows.
How to perform an In-place Upgrade with Windows Step-by-Step *****
https://answers.microsoft.com/en-us/windows/forum/all/how-to-perform-an-in-place-upgrade-with-windows-10/7f0b236e-3c6c-4913-9691-c4baa2a6190a
Hope this resolves your Query!!
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