If the search doesn’t work in the Windows 10 start menu, here’s how to fix it:
Reboot your computer
Start the Windows Search service (set it to auto start)
Restart the Cortana service
Navigate to C:\Windows\System32\WindowsPowerShell\v1.0\ and start PowerShell.exe, then past this code into the PowerShell and hit enter: Get-AppXPackage -AllUsers | Foreach {Add-AppxPackage -DisableDevelopmentMode -Register "$($_.InstallLocation)\AppXManifest.xml"}
Then reboot your computer
Any of the above can make the Start Menu Search start working again, so check if it’s still not working after you’ve tried each option.