Fix Windows Security Service Unavailable in Windows 11 - How to Fix Permission Denied and Version Mismatch in Windows Defender-Troubleshoot PowerShell Startup Error on Windows

Updated 2026-06-15 00:26:02windows-fixes
Fix Windows Security Service Unavailable in Windows 11 - How to Fix Permission Denied and Version Mismatch in Windows Defender-Troubleshoot PowerShell Startup Error on Windows
Before changing system settings, save your work and note the exact error text so you can compare results after each step.

Extra verification checklist

  • Restart the affected app after changing permissions or configuration files.
  • Test the same workflow in a clean browser profile or a temporary user account.
  • Compare the result on another network if the error may be connection related.