Not able to delete VMSS. Seems like an issue with standby pool

Hi,

The guidance from Jilakara is correct. The error indicates that the Standby Pool linked to the VMSS is preventing the deletion from completing.
I just want to add some additional recommendations to complement Jilakara’s response.

Proper fix

1. Delete the associated Standby Pool first
   • Portal: Go to VMSS -> Availability + scale -> Standby pool -> Delete pool
   • CLI:

az standby-vm-pool delete --resource-group <YourResourceGroupName> --name <YourStandbyPoolName>

2. Delete the VMSS

az vmss delete --resource-group <YourResourceGroupName> --name <YourVMSSName> --force-deletion true

Additional recommendations

These steps help handle corner cases that might still cause deletion to fail:

1. Check and register the Standby Pool resource provider

az provider show --namespace Microsoft.StandbyPool --query registrationState -o tsv
az provider register --namespace Microsoft.StandbyPool

• Sometimes the resource provider isn’t registered, or your user lacks permissions, which can cause pool deletion to fail

2. Verify RBAC permissions

• Make sure your account (or service principal) has at least:
  • Microsoft.StandbyPool/*
  • Microsoft.Compute/virtualMachineScaleSets/*
• Usually the Virtual Machine Contributor or Owner role is sufficient

3. If deletion still fails

• Wait until the pool’s state is “Ready” or “Failed” before deleting (not “Deleting” or “Updating”):

az standby-vm-pool list -g <RG_NAME> -o table

• Remove other dependencies such as Capacity Reservation Groups or linked Application Gateway backend pools if attached

Best Regards