MassTransit - Socket exception with AmazonMQ when starting bus

I'm trying to get a basic PoC app running with MassTransit using our Amazon MQ instance, and running into the following problem when I call StartAsync on IBusControl:

MassTransit.ActiveMqTransport.ActiveMqConnectException: Connection exception: (user)@(host) ---> Apache.NMS.NMSConnectionException: Error connecting to (host) ---> System.Net.Sockets.SocketException (0xFFFFFFFE): Unknown error (0xfffffffe) at Apache.NMS.ActiveMQ.Transport.Tcp.TcpTransportFactory.DoConnect(String host, Int32 port, String localAddress, Int32 localPort)

Note: In the exception above, I've edited the items in bold to remove sensitive information. We know that the credentials we are using are in fact correct since we have integration tests for NMS and ActiveMq that use the same credentials. But when trying to connect using MassTransit, we get the above error.

I've tried a number of different approaches but they all produce the same result. Here's some example code to give a general idea of how we're trying to connect:

var busControl = Bus.Factory.CreateUsingActiveMq(configurator =>
            {
                configurator.Host(host, activeMqHostConfigurator =>
                {
                    activeMqHostConfigurator.Username(activeMqConfiguration.UserName);
                    activeMqHostConfigurator.Password(activeMqConfiguration.Password);
                });
            });
await busControl.StartAsync(new CancellationTokenSource(TimeSpan.FromSeconds(10)).Token);

The call to StartAsync is what throws the exception. I have my doubts that this is an issue with MassTransit, it's more likely something that I'm missing but I cannot see what's wrong, and I've had my team review it as well.

As I mentioned in my comment this ended up not being related to MassTransit. It was due to the host being inactive.