VMWare Agentless snapshots fails with "An error occurred while quiescing the virtual machine" (4042840)

• Running a backup with the quiesce option fails with the following message:
  • An error occurred while saving the snapshot: Failed to quiesce the virtual machine.
• VSS Writers go into timeout state after trying to take a quiesced backup.
• Rebooting the VM and trying a quiesce snapshot from vSphere client also fails with the same error.

• The Microsoft VSS providers are reporting a failure. 
• The VMware Snapshot Provider service is not synchronizing with the Microsoft VSS providers.
• The snapshot operation is taking longer than expected.

1. Verify that the VSS providers are in a healthy status by running the following commands on an elevated command prompt:
   1. vssadmin list providers
   2. vssadmin list writers
2. Verify the system event viewer, in order to identify any errors related to the VSS process.
3. Verify that the VMware Snapshot Provider service is not running prior to the backup. 
   1. The VMware Snapshot Provider service only runs on demand when the quiesce snapshot is requested from the backup application or the vSphere client. It will run temporarily and then will stop until the next backup run.

If the VMware Snapshot Provider service stays in running state after trying a backup, as a troubleshooting step, it is possible to temporarily disable this service:

1. In the affected VM, go to services.msc and follow these steps:
   1. Select VMware Snapshot Provider service
   2. Right-click and select Properties.
   3. In startup type select Disable.
2. Reboot the VM to restore the VSS Writers' state.
3. Retry the backup. 

If the backup is successful after disabling the VMware Snapshot Provider service, we can determine that the problem is related to this VMware service. As a workaround, we can keep the VMware Snapshot Provider service disabled, or remove it from VMware Tools completely. It is recommended to investigate this behavior with VMware Support.

To remove the VMware Snapshot provider from VMware Tools:

1. In the Server we want to protect go to Programs and Features:
2. Find VMware Tools | Click Change.
3. In the Wizard that appears click Next | Select Modify | Click Next.
4. Scroll down in the list of features and find Volume Shadow Copy.
5. Click the 'down arrow' and select 'Entire feature will be unavailable'.
6. The icon will change from a drive to an X. Click Next.
7. Confirm by clicking Change.
8. VMware Snapshot Provider service will disappear from services.msc

Please note that upgrading your VMware Tools in the future might override any of these settings.