New
#21
This solved my problem.
I made one small adjustment, however, which was probably only possible because I made the mess myself. I had given the Administrators group ownership and granted Full access for the WindowsApps directory. Windows did not seem to like that.
So because I already had Full access to the WindowsApps folder, I could add the ALL APPLICATION PACKAGES with a Modify grant to just that directory, which immediately allowed me to open the Windows Store, Clock, etc.
Thanks, aza907. You saved me from having to nuke and pave my machine, lol.
Edit: for those curious, WindowsApps is a hidden folder in your %systemroot%\Program Files directory. All your apps from all users are stored in there (as I understand it).