Backup failure, VSS WMI Writer unregistered
Re-register WMI Writer in VSS.
Symptoms / Description
Backup jobs fail due to the VSS WMI Writer being in a failed state. Run "vssadmin info" at the command prompt on the client and look for the following State and Last Error on the WMI Writer. The VSS WMI Writer may have become unregistered.
Writer name: 'WMI Writer'
State:  Failed
To register the VSS WMI Writer: