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Home / developer-tools / Cloudflare Error 521: Web Server Is Down Checklist - How to Resolve MySQL Connection Refused After Restart-How to Resolve Windows Update Proxy Errors After Switching Networks

Cloudflare Error 521: Web Server Is Down Checklist - How to Resolve MySQL Connection Refused After Restart-How to Resolve Windows Update Proxy Errors After Switching Networks

Updated 2026-06-13 13:17:41developer-tools
Cloudflare Error 521: Web Server Is Down Checklist - How to Resolve MySQL Connection Refused After Restart-How to Resolve Windows Update Proxy Errors After Switching Networks
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.

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