Home / office-tools / How to Fix 'ERR_TUNNEL_CONNECTION_FAILED' on Chrome for Mac - Troubleshooting Cloudflare 521 and Nginx Setup-Adding a Private SSL Certificate to Windows Defender Trusted Store

How to Fix 'ERR_TUNNEL_CONNECTION_FAILED' on Chrome for Mac - Troubleshooting Cloudflare 521 and Nginx Setup-Adding a Private SSL Certificate to Windows Defender Trusted Store

Updated 2026-06-13 13:03:15office-tools

How to Fix 'ERR_TUNNEL_CONNECTION_FAILED' on Chrome for Mac - Troubleshooting Cloudflare 521 and Nginx Setup-Adding a Private SSL Certificate to Windows Defender Trusted Store

Prepare

Execute

Validate

Document

Operational follow-up

Record the exact option, command, or setting that changed the result.
Keep a rollback note if the workflow affects shared files or team settings.

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