Using PowerShell to create ‘shared access policies’ on Service Bus QUEUES

I’m struggling to create shared access policies using PowerShell on Service Bus Queues. It works at the Service Bus level but NOT the queue level unless anyone can help?

I have tried:

New-AzureSBAuthorizationRule -Name "Manage" -Namespace $servicebusNamespace -Permission $("Manage", "Listen", "Send") -EntityName $queue -EntityType Queue

and it returns:

New-AzureSBAuthorizationRule : Object reference not set to an instance of an object.

I have also tried various utilising various code snippets calling the .Net assembly Microsoft.ServiceBus.dll e.g.

$CurrentNamespace = Get-AzureSBNamespace -Name $servicebusNamespace
$NamespaceManager = [Microsoft.ServiceBus.NamespaceManager]::CreateFromConnectionString($CurrentNamespace.ConnectionString);
$newkey = [Microsoft.ServiceBus.Messaging.SharedAccessAuthorizationRule]::GenerateRandomKey()
[Microsoft.ServiceBus.Messaging.AccessRights[]] $AccessRights  = [Microsoft.ServiceBus.Messaging.AccessRights]::Send
$AuthorizationRule = [Microsoft.ServiceBus.Messaging.SharedAccessAuthorizationRule]::new("myRule",$newkey, $AccessRights)
$queue = $NamespaceManager.GetQueue($queue)
$queue.Authorization.Add($AuthorizationRule)

Whilst the code executes with no errors, I also don't get any authorization rules!

Can anyone help? Many thanks

Robert