snapshot causing backup to fail

Hello
We have this error ‘[Shadow Copy] Snapshot for Shadow Copy Set is missing, backup terminate’.
The backup has been working ok for 3 months. Today is first error

Hi

If the backup has suddenly stopped working, please check if the backup settings have changed.
In particular the VSS module in this customer’s page in your portal is often a cause of this problem. We see this where housekeeping has been done and the VSS module accidentally removed.

Ahsay OBM 6