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How to Fix Cloudflare 521 Error During Setup - How to Fix Nginx 'Upstream Connection Refused' Error-Windows Security App Not Opening Command Prompt Fix

2026-07-28 06:12:34developer-tools
How to Fix Cloudflare 521 Error During Setup - How to Fix Nginx 'Upstream Connection Refused' Error-Windows Security App Not Opening Command Prompt Fix

Final checklist

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

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