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Windows Security 502 Bad Gateway: Troubleshooting Checklist - How to Fix MySQL Connection Refused on Port 3306-Fix GPG Error in apt update on Ubuntu 22.04

Updated 2026-06-14 15:13:30windows-fixes
Windows Security 502 Bad Gateway: Troubleshooting Checklist - How to Fix MySQL Connection Refused on Port 3306-Fix GPG Error in apt update on Ubuntu 22.04
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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