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Fix Cloudflare Error 521 on Apache Server - Fix Windows Defender DNS Error After Update-Fix Remote Desktop 502 Bad Gateway

2026-06-13 22:37:08developer-tools
Fix Cloudflare Error 521 on Apache Server - Fix Windows Defender DNS Error After Update-Fix Remote Desktop 502 Bad Gateway

Final checklist

  • Confirm that the same symptom is gone after a restart or refresh.
  • Keep the smallest working change and undo temporary diagnostic settings.