Processing VM Error: Unfreeze error (over VIX)

I was checking the backup as a normal daily task, which I understood a virtual machine can not be backed up, so as you can see, based on the error it seems there is a problem with VSS Writer.

Processing VM Name Error: Unfreeze error (over VIX): [Backup job failed.
Cannot create a shadow copy of the volumes containing writer's data.
A VSS critical writer has failed. Writer name: [SqlServerWriter]. Class ID: [{a65faa63-5ea8-4ebc-9dbd-a0c4db26912a}]. Instance ID: [{06128167-948b-4bfe-afc3-1d8cf8b831a9}]. Writer's state: [VSS_WS_FAILED_AT_PREPARE_SNAPSHOT]. Error code: [0x800423f4].]

To get more information about this error, I logged into virtual machines and checked the Event Viewer. I saw that at the same time the backup was running, the following error was displayed in the Windows application log:

SQL Writer error: unexpected error RegOpenKeyExW(FFFFFFFF80000003,S-1-5-21-1644491937-1580436667-1343024091-500\Software\Microsoft\Microsoft SQL Server\90\UserInstance,…). hr = 0x800703fa.

I did some research and finally came across this solution, which comes from Microsoft.

https://docs.microsoft.com/en-us/troubleshoot/windows-server/backup-and-storage/vss-error-8193-restart-cryptographic-services

Run PowerShell as an administrator and run the following command.

$path = 'HKLM:\System\CurrentControlSet\Services\VSS\Diag\'

$sddl = 'D:PAI(A;;KA;;;BA)(A;;KA;;;SY)(A;;CCDCLCSWRPSDRC;;;BO)(A;;CCDCLCSWRPSDRC;;;LS)(A;;CCDCLCSWRPSDRC;;;NS)(A;CIIO;RC;;;OW)(A;;KR;;;BU)(A;CIIO;GR;;;BU)(A;CIIO;GA;;;BA)(A;CIIO;GA;;;BO)(A;CIIO;GA;;;LS)(A;CIIO;GA;;;NS)(A;CIIO;GA;;;SY)(A;CI;CCDCLCSW;;;S-1-5-80-3273805168-4048181553-3172130058-210131473-390205191)(A;ID;KR;;;AC)(A;CIIOID;GR;;;AC)S:ARAI'

$acl = Get-Acl -Path $Path

$acl.SetSecurityDescriptorSddlForm($sddl)

Set-Acl -Path $Path -AclObject $acl

Now try the backup job again, and if you’re as lucky as I was, it should work.

I hope this is informative for you!