windows 11 search box and start menu search turns completly blank and empty after searching something

Since the issue does not happen in a newly created user account, the affected profile is the likely scope. A supported repair path is to reset the Search package data for the affected account.

Try these steps in order:

1. Check for Windows updates Go to Start > Settings > Update & Security > Windows Update > Check for updates. Install any available updates, then restart.
2. Run the Search and Indexing troubleshooter Open Command Prompt and run:

      msdt.exe -ep WindowsHelp id SearchDiagnostic
   

   Select the problems that apply and let Windows attempt repairs.
3. Restart the Windows Search process Since ending SearchHost was already tried, confirm it this way:
   • Press Ctrl+Alt+Delete > Task Manager
   • Open Details
   • Right-click SearchHost.exe and select End task
   • Search again so Windows starts it automatically
   • If needed, restart the PC to also install pending updates
4. Reset Windows Search Resetting Search does not affect files, but search relevance can be temporarily affected.
   • Go to Start > Settings > System > About and confirm the Windows version
   • For Windows 11, use the PowerShell reset method:
     1. Open an elevated PowerShell window
     2. Run:

                Get-ExecutionPolicy
        

     3. If the result is not Unrestricted, record the current value and run:

                Set-ExecutionPolicy -Scope CurrentUser -ExecutionPolicy Unrestricted
        

        Accept the warning by selecting Y.
     4. Download ResetWindowsSearchBox.ps1 and save it locally.
     5. Right-click the script and select Run with PowerShell.
     6. When Done appears, if the execution policy was changed earlier, restore it:

                Set-ExecutionPolicy -Scope CurrentUser -ExecutionPolicy <PreviousValue>
        

5. If only the original account is broken, regenerate the Search AppData folder for that profile This is the strongest profile-specific fix in the documented steps. Warning: this procedure includes deleting a registry key and profile package data. Incorrect registry changes can cause serious problems. Back up the registry first. Steps:
   1. Sign out and use another account, or use Windows Recovery Environment.
   2. Verify Search works in a newly created account.
   3. For Windows 11, delete this folder for the affected profile:

            %USERPROFILE%\AppData\Local\Packages\MicrosoftWindows.Client.CBS\_cw5n1h2txyewy
      

   4. Sign in with the affected account, open Registry Editor, and go to:

            HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Search
      

   5. Delete the Search registry key.
   6. Open an elevated PowerShell window and run:

            Add-AppxPackage -Path "C:\Windows\SystemApps\MicrosoftWindows.Client.CBS_cw5n1h2txyewy\Appxmanifest.xml" -DisableDevelopmentMode -Register
      

   7. Restart the computer.
   8. Test Search again.

That last method matches the symptom that Search works in a different user account but fails in the original one.

References:

• Fix problems in Windows Search