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Fixing ERR_SSL_PROTOCOL_ERROR Certificate Issues - Fix Windows Defender Version Mismatch During Setup-How to Fix Windows Defender Connection Refused Error

Updated 2026-06-13 15:13:28windows-fixes
Fixing ERR_SSL_PROTOCOL_ERROR Certificate Issues - Fix Windows Defender Version Mismatch During Setup-How to Fix Windows Defender Connection Refused Error
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.