Windows Security UI not Launching Completely

Since repair, reset, re-registration, and an in-place installation have already failed, check the active Windows Security platform folder and its file signatures before applying the folder-specific removal fix.

1. Identify the installed platform and invalid files

Open PowerShell as Administrator and run:

Get-ChildItem "C:\Windows\System32\SecurityHealth" -Directory |
    Select-Object Name, FullName

Get-ChildItem "C:\Windows\System32\SecurityHealth\*" -Recurse `
    -Include *.exe,*.dll |
    Get-AuthenticodeSignature |
    Select-Object Status, Path

Look specifically for UnknownError, NotSigned, or another non-Valid status on:

• SecurityHealthHost.exe
• SecurityHealthSSO.dll

This diagnostic identified those two files in a closely matching 26H2 case. A separate matching case used removal of the affected SecurityHealth platform folder after SFC, DISM, Windows Update repair, and other repairs had failed.^1^

2. If the folder is exactly 10.0.29680.1000-0

A matching accepted resolution removed that platform folder and then allowed Windows to restore the Windows Security platform.^2^

Warning: These commands take ownership of and permanently delete that specific system folder. Do not run them against a different version number.

Open Command Prompt as Administrator and run:

cd /d C:\Windows\System32\SecurityHealth
takeown /f 10.0.29680.1000-0 /a /r /d y
icacls 10.0.29680.1000-0 /grant *S-1-5-32-544:(F) /T
rd /s /q 10.0.29680.1000-0
shutdown /r /t 0

After Windows restarts:

1. Open Settings → Windows Update.
2. Select Check for updates and install anything offered.
3. Restart again if requested.
4. Open Windows Security and verify that its dashboard loads.

3. If the folder has another version

Do not substitute its name into the deletion commands. The documented command sequence applies specifically to 10.0.29680.1000-0; another matching case involving older 10.0.29510.1001-0 and 10.0.29554.1001-0 folders used a different repair—copying known-good versions of SecurityHealthHost.exe and SecurityHealthSSO.dll from the older folder.^1^

Record these results for the next version-specific action:

winver
dir C:\Windows\System32\SecurityHealth

Also save the PowerShell signature output from step 1. Post the Windows build, folder names, and the status of SecurityHealthHost.exe and SecurityHealthSSO.dll; those details determine whether folder removal, file replacement, or another platform package is appropriate.

This shield-logo-and-close symptom is not currently listed as a formally recognized Windows 11 26H2 issue on Microsoft’s release-health page, so the unrelated 26H2 Known Issue Rollback for desktop black screens should not be applied.^3^

References

1. The SecurityHealthSystray.exe - Bad Image error - Microsoft Q&A
2. SecurityHealthSystray: SecurityHealthSystray.exe - Bad Image
3. Windows 11, version 26H2 known issues and notifications