Upon backing up a given VM vRanger erros is thrown:
" Unable to continue incremental backup quiesce snapshot not found"
Login to vSphere Client
Right click on VM that is failing to backup and choosing snapshot\ snapshot manger
Check for user created snapshots like ones created via Vmware Update Manager or manually by someone via vSphere Client.
Delete\ remove snapshots
Please note full backups are supported for VMs with existing snapshots via vRanger but incrementals or differentials have never been supported when VMs contain existing snapshots.