The first time a user logs on, there's a long OOBE (Out-Of-Box Experience) process where it installs and configures. Starts with "Hi" and then installs apps. Is it possible to run the thing again, after something has corrupted the user profile? For example, the Start menu quits working. Only fix I have found for something like this is to delete the profile and logon again, unless re-running the OOBE might fix it.
Run PowerShell as admin and run this: Get-AppXPackage -AllUsers | Foreach {Add-AppxPackage -DisableDevelopmentMode -Register "$($_.InstallLocation)\AppXManifest.xml"} It won't re-run the OOBE, but it will re-register all of the modern apps (including the start menu and search).