Azure iot central (cloud) to device

[hubanl]

Hardware: arduino mkr nb1500
Library: GitHub - mjksinc/TIC2019: Code repo for connecting MKRNB 1500 device to Azure IoT Hub as part of the Telstra Innovation Challenge 2019
Cloud: azure iot central

Using the code from the library i am able to send data from device to cloud. Now i am trying to send data from cloud to device to change a threshold value remotely.

In the code setup the following function is created, which print some stuff when a message is received:

  // Set the message callback, this function is
  // called when the MQTTClient receives a message
  mqttClient.onMessage(onMessageReceived);

/*
   Handles the messages received through the subscribed topic and prints to Serial
*/
void onMessageReceived(int messageSize) {

  String topic = mqttClient.messageTopic();

  // when receiving a message, print out the topic and contents
  Serial.print("Received a message with topic '");
  Serial.print(topic);
  Serial.print("', length ");
  Serial.print(messageSize);
  Serial.println(" bytes:");

  // use the Stream interface to print the contents
  while (mqttClient.available()) {
    Serial.print((char)mqttClient.read());
  }
  Serial.println();

  // Responds with confirmation to direct methods and IoT Central commands
  if (topic.startsWith(F("$iothub/methods"))) {
    String msgId = topic.substring(topic.indexOf("$rid=") + 5);

    String responseTopic = "$iothub/methods/res/200/?$rid=" + msgId; //Returns a 200 received message

    mqttClient.beginMessage(responseTopic);
    mqttClient.print("");
    mqttClient.endMessage();
  }
}

When connecting the device to the MQTT broker the following code can be used to subscribe to a topic:

  // subscribe to a topic
  mqttClient.subscribe("devices/" + deviceId + "/messages/devicebound/#"); //This is for cloud-to-device messages
  mqttClient.subscribe("$iothub/methods/POST/#"); //This is for direct methods + IoT Central commands

I would like to subscribe to the topic: testVal. I tried several options, but none of them work.

  // subscribe to a topic
  mqttClient.subscribe("devices/" + deviceId + "/messages/devicebound/testVal"); //This is for cloud-to-device messages
  mqttClient.subscribe("devices/" + deviceId + "/messages/devicebound/#testVal"); //This is for cloud-to-device messages
  mqttClient.subscribe("devices/" + deviceId + "/messages/devicebound/{\"testVal\"}"); //This is for cloud-to-device messages

In the azure iot cloud i am sending the job as shown below:

Does someone know what i am doing wrong?

Thanks in advance!