Hyper-v Windows Server 2012 R2 Standard - vm fails to start

Question

20260225, the host server was rebooted, the vm failed to start, popup displayed;

An error occurred while attempting to start the selected virtual machine.

'Server Name' failed to change state.

The operation failed because the file was not found.

Any help much appreciated.

Answer 1

Hi Chris ,
Thank you for providing the details. After a host reboot, this error typically occurs because the virtual machine is referencing a file that is no longer available or accessible. The most common causes are a mounted ISO file, broken or orphaned checkpoint (AVHDX) chains, or incorrect permissions on virtual disk files.

Recommended resolution steps:

Remove any mounted ISO files Open Hyper‑V Manager → VM Settings → IDE Controller 0 → DVD Drive, eject or remove any mounted ISO files, apply the change, and then start the VM. An inaccessible ISO is a frequent cause of the “operation failed because the file was not found” error after a reboot.

Check and repair checkpoints (AVHDX files) Verify whether the VM has active or orphaned checkpoints. Ensure all AVHDX files have valid parent VHDX paths. Use Hyper‑V Manager or PowerShell to properly merge and remove checkpoints. Broken AVHDX chains, often caused by interrupted backup or merge operations, will prevent the VM from starting.

Verify file permissions Confirm that the VM’s virtual disk folder grants Full Control to the Virtual Machine SID. Missing or incorrect NTFS permissions can block Hyper‑V from accessing VHDX/AVHDX files.

Review VMMS Admin logs Check Event Viewer → Applications and Services Logs → Microsoft → Windows → Hyper‑V‑VMMS → Admin for events that reference the exact missing file path (ISO, VHDX, or AVHDX).

Recovery workaround (if configuration is corrupted) If disk files are healthy but the VM still fails to start, create a new VM with the same generation and attach the existing VHDX. This does not impact the guest OS or licensing and often resolves corrupted VM configuration issues.

If any required disk files are missing or corrupted, restoring them from backup is recommended. Avoid manually editing disk paths unless explicitly directed and always validate checkpoint integrity before deletion.

Please let us know the results after performing these steps or share any VMMS log entries if further assistance is needed.

Best regards,
Nam Bui

Answer 2

Hi Chris ,

Thank you for the information you have already provided. To further narrow down the scope of the issue, could you please help confirm the remaining points below:

• Did the affected VM have any active checkpoints (AVHDX files) before or after the host reboot?
• Is the VM configured with any mounted ISO files, and if yes, are they stored on a local path or shared storage?
• Have there been any recent changes to storage paths, drive letters, or permissions where the VM files are located?
• Do you see any related errors in the Hyper-V VMMS Admin log that reference a missing file path?

These details will help us pinpoint the exact missing dependency and proceed with the appropriate resolution.

Thank you for your cooperation.

Best regards,
Nam Bui