I am trying to experiment with Preview feature available in Azure AKS as per documentation available we need to have the following requirements
- Kubernetes version 1.12.4 or later
- Azure CLI version 2.0.55 or later.
- add aks preview :- az extension add --name aks-preview
- register scale set provider:- az feature register --name VMSSPreview --namespace Microsoft.ContainerService
- ensure that it is registerd

- created AKS cluster with terraform
when i try to apply following command
az aks update --resource-group rg-euwest-d04-dvag-001 --name k8s-euwest-d04-dvag-dfs-dfsapp-001 --enable-cluster-autoscaler --min-count 3 --max-count 5
error
Operation failed with status: 'Bad Request'. Details: AgentPool '' has set auto scaling as enabled but is not on Virtual Machine Scale Sets, this is not allowed