Windows 10 v. 1803 update issue, not resolved by Update Troubleshooter

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.

Installing Windows 10 from USB to replace v. 1803 with v. 1809 resolved the update issue.

However, there were two issues I experienced, and a number of others which have prompted Microsoft to remove the initial Windows 10 v. 1809 update files. In fact, Microsfoft state, “If you have manually downloaded the Windows 10 October 2018 Update installation media, please don’t install it and wait until new media is available."

The issues I faced was complete deletion of images used for background screens (even from Windows.old) and the failure of Windows Notifications to be displayed. Since I had made a disk image prior to updating, I was able to recover lost files. It took considerable time to find the fix for the Action Center.

In Settings | Privacy | Background apps, turn On Let apps run in the background, then reboot for the change to take effect.

Normally, I would not answer my own question, but because of the issues with Windows 10 v. 1809, I'm doing so to let others know of the issue with the first release and of the undocumented change to Notifications and the fix for that.