Messages to Azure Service Bus produce successful requests, but no messages in the queue

Question

I'm attempting to implement a background service in DotNet that sends messages to a queue in Azure Service Bus. My code looks like this:

public class AuditBackgroundService : BackgroundService, IAuditBackgroundService
{
    private readonly TimeSpan _sendInterval;
    private readonly ServiceBusSender _sender;
    private readonly ConcurrentQueue<string> _messageQueue = new ConcurrentQueue<string>();

    public AuditBackgroundService(ServiceBusSender sender, IOptions<AuditConfiguration> config)
    {
        _sendInterval = TimeSpan.FromMilliseconds(config.Value.SendIntervalMilliseconds);
        _sender = sender;
    }

    public void AddMessage(string message)
    {
        _messageQueue.Enqueue(message);
    }

    protected async override Task ExecuteAsync(CancellationToken stoppingToken)
    {
        while (!stoppingToken.IsCancellationRequested)
        {
            await Task.Delay(_sendInterval, stoppingToken);
            await ProcessMessagesAsync(stoppingToken);
        }
    }

    private async Task ProcessMessagesAsync(CancellationToken cancellationToken)
    {
        if (!_messageQueue.IsEmpty)
        {
            while (_messageQueue.TryDequeue(out string message))
            {
                var busMessage = new ServiceBusMessage(message);

                await _sender.SendMessageAsync(busMessage, cancellationToken);
            }
        }
    }
}

As far as I can tell this is working just fine, and indeed from the overview page in Azure I can see I'm getting several successful requests, however no messages are actually hitting the queue.

I've utilized Microsoft's quickstart guide for instructions on how to set up a namespace and a queue for the Azure Service Bus, but despite following the instructions to a t I still can't seem to get it to work. Any idea what I may be doing wrong? Appreciate the help in advance.