For a few weeks, Windows Update has been failing with error 0x80070426 in the Event Log. Despite the warning
Your device is missing important security and quality fixes, no update KB item is listed.
The Windows Update Repair tool finishes with apparent success, but despite repeated attempts, it has not resolved the issue. After running repair, a search for updates produces the dialog above.
The OS is Windows 10 Home version 1803, build 17134.112, and the last updates listed in History are
KB4100347: Intel microcode updates, installed 9/17/2018, and
KB4456655: Servicing stack update for Windows 10, version 1803, installed 9/11/2018. History shows no recent pending or failed update.