MQ131 and BT HC-05 won't work

[orlafn_12213]

I'm currently trying to pair BT HC-05 and this app to show mq131 data. I ve tried a test with another sensor, DHT11, and it worked:

#include <DHT.h>

#define DHTPIN 2 // Pin connected to the DHT sensor
#define DHTTYPE DHT11 // Type of the DHT sensor

DHT dht(DHTPIN, DHTTYPE);

void setup() {
  Serial3.begin(9600); // Initialize Serial3 with a baud rate of 9600
  dht.begin();
}

void loop() {
  delay(2000);
  float h = dht.readHumidity(); // Read humidity
  float t = dht.readTemperature(); // Read temperature in Celsius
  float f = dht.readTemperature(true); // Read temperature in Fahrenheit
  
  // Check if any reads failed
  if (isnan(h) || isnan(t) || isnan(f)) {
    Serial.println("Failed to read from DHT sensor!");
    return;
  }
  
  // Print readings to the Serial3 connection
  Serial3.print(h);
  Serial3.print(",");
  Serial3.print(t);
  Serial3.print(" C,");
  Serial3.print(f);
  Serial3.print(" F;");
  
  delay(2000); // Adjust delay according to your needs
}
!

But when it comes to mq131, i got no results:

#include <MQ131.h>

void setup() {
  Serial3.begin(9600); // Initialize Serial3 with a baud rate of 9600
  MQ131.begin(2,A1, LOW_CONCENTRATION, 1000000); 
  MQ131.calibrate();
  
}

void loop() {
  delay(2000);
  MQ131.sample();
  MQ131.getO3(PPM);
  MQ131.getO3(PPB);
  MQ131.getO3(MG_M3);
  float mq131 = MQ131.getO3(UG_M3);
  Serial3.print(mq131);
  Serial3.print(",");
  Serial3.print("ug/m3");
  Serial3.print(";");
  

  delay(2000); // Adjust delay according to your needs
}

But there's no shown data on the app.
What could have gone wrong?