Error while authenticating. The operation has timed out

[Resultfactory]

Hi and compliments on this great sample! We are trying to build the same architecture using hivemq and MQTTnet but when trying to connect to the hivemq broker on :1883 we keep getting an error 'Error while authenticating. The operation has timed out'. Where can we check what is wrong?
var options = new MqttClientOptionsBuilder()
.WithTcpServer("192.168.1.109", 1883)
.WithClientId("bst-001")
.WithCleanSession()
.Build();

            // handlers
            _client.ConnectedAsync += OnConnectedAsync;
            _client.ConnectingAsync += _client_ConnectingAsync;
            _client.DisconnectedAsync += OnDisconnectedAsync;
            _client.ApplicationMessageReceivedAsync += OnApplicationMessageReceivedAsync;

            // connect
            await _client.ConnectAsync(options);