SIP Trunk registration fails with 408 Request Timeout during Zendesk Voice migration

  • Genesys Cloud Org: EU-West-1
  • SIP Trunk Type: On-Premises Gateway
  • Gateway Firmware: 12.5.3
  • Zendesk Voice Legacy: On-prem PBX integration

Why does this setting cause the SIP trunk to drop registrations immediately after enabling the ‘Require Secure Registration’ flag? The gateway logs show a 408 Request Timeout, which feels like the strict TLS handshake we struggled with when moving Zendesk Voice to cloud, but the certs are valid. Need a workaround to keep the migration timeline on track.