I have a user that reported not being able to use Windows 10's search function. Any apps that she had installed were not appearing there. Things included in Windows 10 (like Settings) were being found. Another weird quirk is that old utilities like Control Panel can't be opened from Start menu. They open just fine by clicking on the shortcut or the control command from Run.
I've rebuilt the index, ran Get-AppXPackage -Name Microsoft.Windows.Cortana | Foreach {Add-AppxPackage -DisableDevelopmentMode -Register "$($_.InstallLocation)\AppXManifest.xml"}, restarted Explorer. Nothing has changed.
I plan on trying what harrymc reccomends in this thread and will update if that works.
