Windows Security won't open on Windows 11

Fix plan (in order)

Step 1 — Try to restore the missing service via SFC/DISM

powershell

DISM /Online /Cleanup-Image /RestoreHealth sfc /scannow

Restart, then check services.msc again for "Windows Security Health Service."

Step 2 — Re-register the Security Health service manually
If it's still missing after step 1, open PowerShell as Admin:

powershell

sc.exe create SecurityHealthService binPath= "%windir%\System32\SecurityHealthService.exe" start= demand

(Only run this if the .exe still exists at C:\Windows\System32\SecurityHealthService.exe — check first with dir C:\Windows\System32\SecurityHealthService.exe.)

Step 3 — Remove the leftover PunkBuster service

powershell

sc.exe delete PnkBstrA

(Check for PnkBstrB too — run sc.exe query | findstr /i pnkbstr to see all variants.) Also delete the folder at C:\Program Files (x86)\Common Files\PunkBuster if it's still there and no other game needs it.

Step 4 — Re-register the Security Center app package

powershell

Get-AppxPackage -allusers Microsoft.Windows.SecHealthUI | Foreach {Add-AppxPackage -DisableDevelopmentMode -Register "$($_.InstallLocation)\AppXManifest.xml"}

Step 5 — Restart and check
Reboot, then open Windows Security again.