I have two sets of ESP-32 and Ra-02 LoRa module. I want to send a message from one node to the other and get the reply back. Sending a message from node1 to node2 reaches node2. But sending the reply message from node2 to node1 is not happening. Am I missing something here.

Node1 code:

#include <SPI.h>
#include <LoRa.h>

#define SCK 18
#define MISO 19
#define MOSI 23
#define NSS 5
#define RESET 14
#define DIO0 26

void setup() {
  Serial.begin(115200);
  while (!Serial);

  LoRa.setPins(NSS, RESET, DIO0);
  if (!LoRa.begin(433E6)) {
    Serial.println("Starting LoRa failed!");
    while (1);
  }

  Serial.println("LoRa Transmitter");
}

void loop() {
  String message = "Hello";
  Serial.print("Sending: ");
  Serial.println(message);
  
  LoRa.beginPacket();
  LoRa.print(message);
  LoRa.endPacket();

  delay(100); // Brief delay to ensure packet is sent

  // Wait for acknowledgment
  unsigned long startMillis = millis();
  unsigned long timeout = 2000; // 2 seconds timeout
  String response = "";

  LoRa.idle(); // Ensure the module is in idle state before entering the loop
  while (millis() - startMillis < timeout) {
    int packetSize = LoRa.parsePacket();
    if (packetSize) {
      while (LoRa.available()) {
        response += (char)LoRa.read();
      }
      break; // Exit the loop once a packet is received
    }
  }

  if (response != "") {
    Serial.print("Received response: ");
    Serial.println(response);
  } else {
    Serial.println("No response received");
  }

  delay(5000); // Wait for 5 seconds before the next loop
}

Node2 code:

#include <SPI.h>
#include <LoRa.h>

#define SCK 18
#define MISO 19
#define MOSI 23
#define NSS 5
#define RESET 14
#define DIO0 26

void setup() {
  Serial.begin(115200);
  while (!Serial);

  LoRa.setPins(NSS, RESET, DIO0);
  if (!LoRa.begin(433E6)) {
    Serial.println("Starting LoRa failed!");
    while (1);
  }

  Serial.println("LoRa Receiver");
}

void loop() {
  int packetSize = LoRa.parsePacket();
  if (packetSize) {
    String incoming = "";
    while (LoRa.available()) {
      incoming += (char)LoRa.read();
    }

    Serial.print("Received: ");
    Serial.println(incoming);

    // Send acknowledgment
    String response = incoming + ":ack";
    Serial.print("Sending: ");
    Serial.println(response);
    
    LoRa.beginPacket();
    LoRa.print(response);
    LoRa.endPacket();
  }
}