Windows 10 search not working - SearchUI.exe missing

Microsoft provided a solution to reset Windows search via a powershell script and a set of steps found here under "Reset Windows Search." I'm including the steps as well as the contents of the powershell script "ResetWindowsSearchBox.ps1" below.

If the Windows 10 May 2019 Update or a later update is installed, use Windows PowerShell to reset Windows Search. To do this, follow these steps.

Note You must have administrator permissions to run this script.

1. Click the Download button and save ResetWindowsSearchBox.ps1 to a local folder.
2. Right-click the file that you saved, and select Run with PowerShell.
3. If you are asked "Do you want to allow this app to make changes to your device?," select Yes.
4. The PowerShell script resets the Windows Search feature. When the word "Done" appears, close the PowerShell window.

5. If you receive a "Cannot be loaded because running scripts is disabled on this system" error message, enter the following command on the command line of the PowerShell window, and then press Enter:

   Get-ExecutionPolicy

   Note The current policy appears in the window. For example, you might see Restricted. We recommend that you note this value because you'll have to use it later.

6. Enter the following command on the command line of the PowerShell window, and then press Enter:

   Set-ExecutionPolicy -Scope CurrentUser -ExecutionPolicy Unrestricted

   Note You'll receive a warning message that explains the security risks of an execution policy change. Press Y, and then press Enter to accept the change. To learn more about PowerShell execution policies, see About Execution Policies.

7. After the policy change is completed, close the window, and then repeat steps 2–4. However, when the "Done" message appears this time, DON'T close the PowerShell window. Instead, press any key to continue.

8. Revert to your previous PowerShell execution policy setting. To do this, enter the following command on the command line of the PowerShell window, press the Spacebar, enter the policy value that you noted in step 5, and then press Enter:

   Set-ExecutionPolicy -Scope CurrentUser -ExecutionPolicy

   For example, if the policy that you noted in step 5 was Restricted, the command would resemble the following:

   Set-ExecutionPolicy -Scope CurrentUser -ExecutionPolicy Restricted

   Note You'll receive a warning message that explains the security risks of an execution policy change. Press Y, and then press Enter to accept the change and revert to your previous policy setting.

9. Close the PowerShell window.

[10. Restart PC]¹

Note If your organization has disabled the ability to run scripts, contact your administrator for help.

¹ Added step 10 since this fix didn't take effect until I restarted.

ResetWindowsSearchBox.ps1

# Copyright © 2019, Microsoft Corporation. All rights reserved.

function T-R
{
    [CmdletBinding()]
    Param(
        [String] $n
    )

    $o = Get-Item -LiteralPath $n -ErrorAction SilentlyContinue
    return ($o -ne $null)
}

function R-R
{
    [CmdletBinding()]
    Param(
        [String] $l
    )

    $m = T-R $l
    if ($m) {
        Remove-Item -Path $l -Recurse -ErrorAction SilentlyContinue
    }
}

function S-D {
    R-R "HKLM:\SOFTWARE\Microsoft\Cortana\Testability"
    R-R "HKLM:\SOFTWARE\Microsoft\Search\Testability"
}

function K-P {
    [CmdletBinding()]
    Param(
        [String] $g
    )

    $h = Get-Process $g -ErrorAction SilentlyContinue

    $i = $(get-date).AddSeconds(2)
    $k = $(get-date)

    while ((($i - $k) -gt 0) -and $h) {
        $k = $(get-date)

        $h = Get-Process $g -ErrorAction SilentlyContinue
        if ($h) {
            $h.CloseMainWindow() | Out-Null
            Stop-Process -Id $h.Id -Force
        }

        $h = Get-Process $g -ErrorAction SilentlyContinue
    }
}

function D-FF {
    [CmdletBinding()]
    Param(
        [string[]] $e
    )

    foreach ($f in $e) {
        if (Test-Path -Path $f) {
            Remove-Item -Recurse -Force $f -ErrorAction SilentlyContinue
        }
    }
}

function D-W {

    $d = @("$Env:localappdata\Packages\Microsoft.Cortana_8wekyb3d8bbwe\AC\AppCache",
        "$Env:localappdata\Packages\Microsoft.Cortana_8wekyb3d8bbwe\AC\INetCache",
        "$Env:localappdata\Packages\Microsoft.Cortana_8wekyb3d8bbwe\AC\INetCookies",
        "$Env:localappdata\Packages\Microsoft.Cortana_8wekyb3d8bbwe\AC\INetHistory",
        "$Env:localappdata\Packages\Microsoft.Windows.Cortana_cw5n1h2txyewy\AC\AppCache",
        "$Env:localappdata\Packages\Microsoft.Windows.Cortana_cw5n1h2txyewy\AC\INetCache",
        "$Env:localappdata\Packages\Microsoft.Windows.Cortana_cw5n1h2txyewy\AC\INetCookies",
        "$Env:localappdata\Packages\Microsoft.Windows.Cortana_cw5n1h2txyewy\AC\INetHistory",
        "$Env:localappdata\Packages\Microsoft.Search_8wekyb3d8bbwe\AC\AppCache",
        "$Env:localappdata\Packages\Microsoft.Search_8wekyb3d8bbwe\AC\INetCache",
        "$Env:localappdata\Packages\Microsoft.Search_8wekyb3d8bbwe\AC\INetCookies",
        "$Env:localappdata\Packages\Microsoft.Search_8wekyb3d8bbwe\AC\INetHistory",
        "$Env:localappdata\Packages\Microsoft.Windows.Search_cw5n1h2txyewy\AC\AppCache",
        "$Env:localappdata\Packages\Microsoft.Windows.Search_cw5n1h2txyewy\AC\INetCache",
        "$Env:localappdata\Packages\Microsoft.Windows.Search_cw5n1h2txyewy\AC\INetCookies",
        "$Env:localappdata\Packages\Microsoft.Windows.Search_cw5n1h2txyewy\AC\INetHistory")

    D-FF $d
}

function R-L {
    [CmdletBinding()]
    Param(
        [String] $c
    )

    K-P $c 2>&1 | out-null
    D-W # 2>&1 | out-null
    K-P $c 2>&1 | out-null

    Start-Sleep -s 5
}

function D-E {
    Write-Host "Press any key to continue..."
    $Host.UI.RawUI.ReadKey("NoEcho,IncludeKeyUp") > $null
}

Write-Output "Verifying that the script is running elevated"
if (-Not ([Security.Principal.WindowsPrincipal] [Security.Principal.WindowsIdentity]::GetCurrent()).IsInRole([Security.Principal.WindowsBuiltInRole] 'Administrator')) {
 if ([int](Get-CimInstance -Class Win32_OperatingSystem | Select-Object -ExpandProperty BuildNumber) -ge 6000) {
  $Cx = "-File `"" + $MyInvocation.MyCommand.Path + "`" " + $MyInvocation.UnboundArguments
  Start-Process -FilePath PowerShell.exe -Verb Runas -ArgumentList "-noexit",$Cx
  Exit
 }
}

$a = "searchui"
$b = "$Env:localappdata\Packages\Microsoft.Windows.Search_cw5n1h2txyewy"
if (Test-Path -Path $b) {
    $a = "searchapp"
} 


Write-Output "Resetting Windows Search Box"
S-D 2>&1 | out-null
R-L $a

Write-Output "Done..."
D-E

I managed to restore the search function by running the Windows 10 setup that can be downloaded via Microsoft's Media Creation Tool which can be obtained from this website. As also mentioned in this Reddit post, create a system restore point before you run that setup in case anything goes wrong in the process. Rather safe than sorry.

The steps that I did to restore my system are:

1. Download and run the Media Creation Tool.
2. Select "Create installation media for another PC" and press the "Next" button.
3. Tick the "Use the recommended options for this PC" checkbox (if it's not ticked already) and press the "Next" button.
4. Select "ISO file" and press the "Next" button.
5. Provide a path where the ISO file should be saved and confirm.
6. Wait for the download to finish. Once it's done, go to the download location.
7. Right-click the ISO file and press "Mount". The Windows Explorer should switch to a mounted drive which contains, among other files, a setup.exe.
8. Run setup.exe.
9. Decide whether or not you'd like to download and install all available Windows Updates before you proceed. I for my part decided to update, which is also marked as the recommended option. Press "Next".
10. If the setup asks you which files to keep, select the option that keeps your files and installed applications.
11. Wait for the setup to finish. Your computer will be rebooted at least once in the process.
12. (optional) Uninstall any preinstalled applications that you don't want installed.