Fix Windows Security Invalid Configuration Error - How to Fix Outlook Keeps Asking for Password on Windows-Resolve Cloudflare 521 on Apache Server

Updated 2026-06-18 04:31:38office-tools
Fix Windows Security Invalid Configuration Error - How to Fix Outlook Keeps Asking for Password on Windows-Resolve Cloudflare 521 on Apache Server
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.