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How to Fix Nginx 'Upstream Connection Refused' Error - Fix Edge Sync Not Syncing Tabs Across Devices-Fix 521 Error with Cloudflare Origin Pull Configuration

Updated 2026-07-28 10:26:17browser-issues
How to Fix Nginx 'Upstream Connection Refused' Error - Fix Edge Sync Not Syncing Tabs Across Devices-Fix 521 Error with Cloudflare Origin Pull Configuration
Likely symptom
Likely cause
Safe rollback

Verification route

  • Repeat the original action, not only a simplified test case.
  • Restart the app or reload the service after configuration changes.