HCX Bulk Migration Fails During Initial Sync After On-Premises vCenter Certificate Replacement - "Initial Sync Failed: Replication transfer failed with unknown error."

Products

• VMware HCX

Issue/Introduction

• After replacing the SSL certificates (VMCA-ROOT/Machine SSL/ Soultion Users Certificate) on the on-premises vCenter Server, VMware HCX Bulk Migrations fail during the initial synchronization phase.
• The HCX UI displays the following error message for the failed migration:
  "Initial Sync Failed: Replication transfer failed with unknown error."
  
  
  
  
• The app.log file on the on-premises (source) HCX Manager, located at /common/logs/admin/app.log, reports an error refreshing the vCenter connection:
  2026-03-05 03:15:33.731 UTC [pool-10-thread-1, , , TxId: ] ERROR c.v.v.h.a.v.VCenterAdapterFactory- Error refreshing vc connection.
java.lang.NullPointerException: null
• Additionally, the app.log file on the target HCX Manager (/common/logs/admin/app.log) may report a communication failure indicating that the Host-Based Replication (HBR) server is unreachable:
  2026-03-05 04:10:33.384 UTC [ReplicationTransferService_SvcThread-10267, Ent: HybridityAdmin, , TxId: TxId: ######-####-#####-##########] INFO  c.v.h.s.r.utils.VrServerAdapterUtil- Creating new adapter instance for the HBR server '<IX_Appliance_IP>'
2026-03-05 04:10:33.482 UTC [ReplicationTransferService_SvcThread-10267, Ent: HybridityAdmin, , TxId: TxId: #######-###-####-#####-#########] ERROR c.v.h.s.r.jobs.SetupTarget- Job ( #######-###-####-#####-#########) failed with exceptionjava.lang.RuntimeException: Error Running request
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Caused by: com.vmware.vchs.hybridity.adapters.hbr.fault.HbrServiceNotReachableException: Error communicating to HBR server <IX_Appliance_IP>:8123. Reason: Service Unavailable

Environment

VMware HCX

Cause

• Stale vCenter Registration: The connection between the Source HCX Manager and the Source vCenter is broken because the HCX Manager still holds the old vCenter certificate.
• Stale Thumbprint on the IX Appliance: Even after a Service Mesh resync, the new vCenter certificate thumbprint fails to update automatically on the Interconnect (IX) appliance, causing the replication service (hbrsrv) to become unavailable.

Resolution

To resolve this issue, we must manually update the vCenter certificate on the Source HCX Manager and restart the replication service on the IX appliance.

• For error : 
  "ERROR c.v.v.h.a.v.VCenterAdapterFactory- Error refreshing vc connection.
java.lang.NullPointerException: null"
  • Re-register the Source vCenter
    • Log in to the Source HCX Appliance Management Interface at https://<Source-HCX-Manager-IP>:9443.
    • Navigate to the vCenter Server registration section under 'Dashboard'.
    • Edit the vCenter configuration, re-enter the administrator credentials and save.
    • Accept the new vCenter certificate prompt to re-establish the connection.
      
      
• For error:
  Error communicating to HBR server <IX_Appliance_IP>:8123. Reason: Service Unavailable.
  • Restart the HBR Service on the IX Appliance
    • SSH to IX appliance via the HCX Manager appliance.
    • Execute the following command to restart the Host-Based Replication service:
      • systemctl restart hbrsrv
    • Verify the service is running correctly:
      • systemctl status hbrsrv
    • Retry the Bulk Migration from the HCX UI. The initial sync should now proceed successfully.