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Fixing Cloudflare 521 Error with Nginx Configuration - Fix Chrome ERR_TUNNEL_CONNECTION_FAILED Error-WireGuard Handshake Not Completing: Practical Checklist

2026-06-13 13:07:16windows-fixes
Fixing Cloudflare 521 Error with Nginx Configuration - Fix Chrome ERR_TUNNEL_CONNECTION_FAILED Error-WireGuard Handshake Not Completing: Practical Checklist

Final checklist

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