If you can't type in the Windows 10 start menu or Cortana search bar then it's possible a key service is disabled or an update has caused an issue. 

Before proceeding below there are some prerequisites

• Administrator rights required
• Firewall enabled

There are two methods, the first method typically solves the issue.

Before proceeding try searching after firewall has been enabled.  It's possible enabling the firewall will resolve the issue.  If not proceed below.

Method 1:

• Press Windows + X keys on the keyboard, select Command prompt (admin).

• Enter the below commands one by one and hit Enter key.

  PowerShell -ExecutionPolicy Unrestricted

• It will turn the command prompt into a PowerShell window.

• Now cut and paste the following command below and hit Enter key.

  Get-AppXPackage -AllUsers |Where-Object {$_.InstallLocation -like "*SystemApps*"} | Foreach {Add-AppxPackage -DisableDevelopmentMode -Register "$($_.InstallLocation)\AppXManifest.xml"}

• Reboot and the issues should be resolved

If the issue still persist, follow the below method.

Method 2:

• Open the Task manager.  Here’s a tip:  Press CTRL+Shift+ESC.
• Click File > Run New Task
• Make sure you have a check mark beside “Create this task with administrative privileges”
• Type Powershell
• Type the following in the Powershell prompt:
  $manifest = (Get-AppxPackage Microsoft.WindowsStore).InstallLocation + '\AppxManifest.xml' ; Add-AppxPackage -DisableDevelopmentMode -Register $manifest

• Close the Powershell window
• Reboot the computer and check if it helps.