"Virtual Machine is unavailable and will be skipped from processing. " or "Failed to expand object"

These errors occur when the hypervisor fails to locate the Virtual Machine (VM) based on the reference ID that Veeam Backup & Replication  (VBR) provided. When a VM is processed by a VBR job, that VM is tracked by the backend hypervisor reference ID to ensure that even if the machine is renamed or another VM is built with the same name, VBR will always protect the correct VM.

• In a vSphere environment, this unique reference ID is called a Managed Object Reference ID, or MORef-ID.
• In a Hyper-V environment, the unique reference ID is called a Virtual Machine ID, or VMID.

• The resolution can be confirmed without running the job. Edit the job, navigate to the "Virtual Machines" tab, and click the [Recalculate] button. Note that the VM(s) whose reference ID(s) changed now report as having the correct size.
• The most common events that cause a VM's reference ID to change are:
  • For vSphere Environments:
    •  A VM is removed from inventory and then added back to inventory.
    • In rare cases, a host crash, which prompts the host to be removed and added back to the vCenter, may cause the VMs on that host to get new MoRef-IDs.
    • Reinstallation or creating a new vCenter server where the old database is not reused will cause all objects managed by the vCenter to receive new unique identifiers.
      Customers are encouraged to utilize the vCenter's native file-based backup to protect and restore the configuration, ensuring unique reference IDs are preserved.
  • For Hyper-V Environments:
    • A VM is exported and reimported.