UPDATE: Fixed. It was one of the two steps in red below followed by a reboot.
I am running Windows 10 Professional 1709. Fully patched with all available patches from Windows Update.
At least in the past two days, I've been unable to update or install anything from the Microsoft Store. All app updates or installs of new apps (!) result in a 0x80073CF9 error code.
What I have done so far (none have fixed the problem):
- Created or verified existence of C:\Windows\AppReadiness and C:\Windows\AUInstallAgent.
- Ran the troubleshooter for Windows apps (https://support.microsoft.com/en-ph/help/4027498/windows-10-run-the-troubleshooter-for-apps). No problems found.
- Ran the Windows Update troubleshooter (https://support.microsoft.com/en-us/help/2714434/description-of-the-windows-update-troubleshooter). No problems found.
- Ran sfc /scannow in a command prompt window as administrator. No problems found.
- Ran WSReset.exe.
- Ran the PowerShell script suggested by Robelene Win below.
- Created the C:\Windows\System32\AppLocker folder.
Every time I attempt to download a new app (in this case, Microsoft To-Do), I get errors in my Windows Application event log with these event names, in this order:
I'm unclear how to fix. Frankly, all I can find are the usual Microsoft-affiliated trolls whose canned responses rarely help.