Azure VM scale sets not accessible and cannot restart - azure

Question

Today, I found I cannot remote into my Azure VM scale set instances (win 2016 Nano Server). I then tried restart the VM scale set instance using powershell but got following like error:
Restart-AzureRmVmss : Long running operation failed with status 'Failed'. Additional Info:'VM 'master-vmss_0' has not
reported status for VM agent or extensions. Please verify the VM has a running VM agent, and can establish outbound
connections to Azure storage.'
ErrorCode: VMAgentStatusCommunicationError
ErrorMessage: VM 'master-vmss_0' has not reported status for VM agent or extensions. Please verify the VM has a
running VM agent, and can establish outbound connections to Azure storage.
Our VM scale sets has been running correctly for nearly one year. What happened on VMSS? Did Azure make changes on VMSS recently?
Update with NSG outbound rule:
{
"name": "AllowVnetOutBound",
"properties": {
"provisioningState": "Succeeded",
"description": "Allow outbound traffic from all VMs to all VMs in VNET",
"access": "Allow",
"priority": 65000,
"direction": "Outbound",
}
},
{
"name": "AllowInternetOutBound",
"properties": {
"provisioningState": "Succeeded",
"description": "Allow outbound traffic from all VMs to Internet",
"access": "Allow",
"priority": 65001,
"direction": "Outbound",
}
},
{
"name": "DenyAllOutBound",
"etag": "W/\"a8e5e396-4f92-4118-b8ea-9b7d0111079f\"",
"properties": {
"provisioningState": "Succeeded",
"description": "Deny all outbound traffic",
"access": "Deny",
"priority": 65500,
"direction": "Outbound",
}
}

Answer 1

Check Network Security Group is blocking outbound connectivity from your VM?
VM Agent and Extensions are updated
If HTTPS is blocked to this storage account then you will get this error message. More information here http://www.deployazure.com/compute/virtual-machines/azure-vm-agent-extensions-deep-dive-part-3/

Answer 2

Our VM scale sets has been running correctly for nearly one year. What
happened on VMSS? Did Azure make changes on VMSS recently?
Recently, there are some maintenance in Azure, update host OS to windows server 2016. We can find the maintenance information in Azure portal, like this:
In your scenario, maybe we can create a new VM in VMSS' vnet, then use that VM to remote the VMSS instance, to check the VM agent status.
If the VM agent status is down, we should start it.
Update:
Recently you experienced an issue with starting VM failure after planned maintenance VM reboot. This is due to container fault issue in the backend.
Our backend engineer has checked the faulted tenant and applied mitigation. Can you try to restart the VMss again? If that does not work, please create a support ticket to Azure.
Again, sorry for all the inconvenience caused for you.