Publish and Subscribe not working when using PRIVATE / MY_DEVICES

Hello,

I have 2 photons up and running, with one publishing events, and the other subscribing to them. Everything works fine until I add the PRIVATE / MY_DEVICES parameters, respectively. The active parts of my code are show below. If you see something wrong, your help would be greatly appreciated!

PUBLISHING DEVICE CODE:

double voltage = 0;
double waterlevel = 0;

void setup() {
    pinMode(A0, INPUT);
}

void loop() {

    voltage = analogRead(A0);
    waterlevel = voltage / 220; 
    Particle.publish("WaterLevelPublish", String(waterlevel), PRIVATE);
    delay(30000);       
}

SUBSCRIBING DEVICE CODE

int water_level_int = 0; 
Adafruit_8x8matrix matrix; 

void myHandler(const char *event, const char *data)
{
  std::string num = data;
  double temp = ::atof(num.c_str());
  water_level_int = (int)temp;
}

void setup() {
  Serial.begin(9600);
  Serial.println("8x8 LED Matrix Test");
  matrix.begin(0x70); 
  Particle.subscribe("WaterLevelPublish", myHandler, MY_DEVICES);
}

void loop() {

// This loop blinks an 8x8 LED matrix based on the value of water_level_int 

}

After rebooting each device several times, things seem to be working now.