Fix Windows Defender Not Opening Error 404 - Windows Security Cache Clearing Guide-Fix OneDrive 504 Gateway Timeout: Setup & Troubleshooting Guide

Updated 2026-06-13 22:46:47browser-issues
Fix Windows Defender Not Opening Error 404 - Windows Security Cache Clearing Guide-Fix OneDrive 504 Gateway Timeout: Setup & Troubleshooting Guide
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.