You must add to the backup infrastructure file shares that you plan to use as source for backup.
You can add file share of the following types:
Reading from VSS snapshots is available only if the following conditions are met:
- The source file share is running on the machine with SMB v3 feature enabled.
- The file proxy role is assigned to the machine running Microsoft Windows Server 2012 R2 or later with SMB v3 feature enabled.