"You'll need a new app to open this windowsdefender link" fix

1. launch powershell as an admin}
2. run get-AppxPackage Microsoft.SecHealthUI -AllUsers | Reset-AppxPackage

Worked for me.

Windows 11 Pro 21H2 22000.708

You can choose yes. This is a great fix for single accounts with admin privileges. If you have sub accounts though (non-admin accounts for family members), this won't fix it. You'll need to create local accounts, then copy their data from their microsoft account into the local, then delete the microsoft account, and then scour the internet to find fixes for why there's permission errors, and then open a new Microsoft ticket to troubleshoot that, and then be told to reinstall Windows 11 again, and recreate all of the profiles from scratch.

I regret upgrading to Windows 11.

Hi this post is to help people with windows 10 and 11 windows security not working

On windows 11 do this

1. launch powershell as an admin
2. Set-ExecutionPolicy Unrestricted
3. Get-AppXPackage -AllUsers | Foreach {Add-AppxPackage -DisableDevelopmentMode -Register "$($_.InstallLocation)\AppXManifest.xml"}
4. Set-ExecutionPolicy restricted

IGNORE THE ERRORS

on windows 10 do this

1. launch powershell as an admin}
2. run get-AppxPackage Microsoft.SecHealthUI -AllUsers | Reset-AppxPackage
3. if it doesn't work do this
   4) run Add-AppxPackage -Register -DisableDevelopmentMode "C:\Windows\SystemApps\Microsoft.Windows.SecHealthUI_cw5n1h2txyewy\AppXManifest.xml"
4. run get-AppxPackage Microsoft.SecHealthUI -AllUsers | Reset-AppxPackage

I was having this problem on Windows 11 after I upgraded from Windows 10. I followed the direction for fixing the problem on Windows 11 using PowerShell as an administrator and this procedure did resolve my problem ever thing is working fine now.

Can anyone confirm that this fixes secondary accounts (non-admin)? I'm having no luck getting it fixed. The funny part is, after yesterday's updates for Win 11, the orange notification has turned green again, but it still gives the same message that WindowsDefender is missing.

I had this same problem. Admin account and standard account on the PC - logged in as standard user, running powershell as admin. The above instructions did not work. No change.

I turned my standard user account into an admin (computer management, users & groups, users, user account's properties, "member of" tab, added Administrators). Restarted and reran the above instructions while logged in as that user who is now an admin. That worked.

I haven't removed the user from the admin group yet, but I'm hoping the fix will continue to work.