Windows 10 apps will not start

Just upgraded my Windows 8.1 Pro (Lenovo W540 laptop) to Windows 10, everything went smoothly, all my settings and installed apps preserved and work without a hitch.

The only issue is - Windows's own apps - Calendar, Mail etc. even Windows AppStore - won't launch. When I run them I very briefly see a window flashing and then nothing happens after that.

Any idea what's going on and how to fix it?

EDIT: Seeing bunch of these in Event log: Activation of app Microsoft.WindowsStore_8wekyb3d8bbwe!App failed with error: Access is denied. See the Microsoft-Windows-TWinUI/Operational log for additional information.

Solution 1:

Figured it out. For some reason ALL APPLICATION PACKAGES account lost access to C:\Program Files\WindowsApps folder. Once I added it - problem was solved, appstore apps launch normally.

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