#define BLYNK_PRINT Serial
#define BLYNK_TEMPLATE_ID "*****"
#define BLYNK_TEMPLATE_NAME "****"
#define BLYNK_AUTH_TOKEN "****"

#include <ESP8266WiFi.h>
#include <WiFiClient.h>
#include <PubSubClient.h>
#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include "DHT.h"
#include <BlynkSimpleEsp8266.h>

#define DHTPIN D5
#define rainpin A0
#define DHTTYPE DHT11
DHT dht(DHTPIN, DHTTYPE);

const char* ssid = "*****";
const char* password = "****";
const char* mqtt_server = "broker.hivemq.com";

WiFiClient espClient;
PubSubClient client(espClient);
LiquidCrystal_I2C lcd(0x27, 16, 2);

char auth[] = "*****";

float t, h;
int rain;
String rainstatus;
char tempBuffer[10], humBuffer[10], rainBuffer[50];
long lastReconnectAttempt;

void callback(char* topic, byte* payload, unsigned int length) {
  String message = "";
  for (int i = 0; i < length; i++) {
    message += (char)payload[i];
  }

  Serial.print("Message received on topic: ");
  Serial.print(topic);
  Serial.print(". Message: ");
  Serial.println(message);

  if (strcmp(topic, "proj/temperature") == 0) {
    t = message.toFloat();
    Blynk.virtualWrite(0, t);
  } else if (strcmp(topic, "proj/humidity") == 0) {
    h = message.toFloat();
    Blynk.virtualWrite(1, h);
  } else if (strcmp(topic, "proj/rain_status") == 0) {
    rainstatus = message;
    Blynk.virtualWrite(2, rainstatus);
  }
}

boolean reconnect() {
  if (client.connect("ESP8266Client")) {
    Serial.println("MQTT Connection Established");
    client.subscribe("proj/temperature");
    client.subscribe("proj/humidity");
    client.subscribe("proj/rain_status");
  }
  return client.connected();
}

void setup() {
  Serial.begin(9600);
  pinMode(rainpin, INPUT);
  dht.begin();

  client.setServer(mqtt_server, 1883);
  client.setCallback(callback);

  lcd.init();
  lcd.backlight();
  lcd.print("  IoT WEATHER");
  lcd.setCursor(0, 1);
  lcd.print("    STATION");
  delay(2000);
  lcd.clear();
  lcd.setCursor(1, 0);
  lcd.print("CONNECTING TO");
  lcd.setCursor(3, 1);
  lcd.print("INTERNET");
  Blynk.begin(auth, ssid, password);
  lcd.clear();
  lcd.setCursor(2, 0);
  lcd.print("CONNECTED TO");
  lcd.setCursor(3, 1);
  lcd.print("INTERNET");
  delay(2000);

  lastReconnectAttempt = 0;
}

void loop() {
  if (!client.connected()) {
    long now = millis();
    if (now - lastReconnectAttempt > 5000) {
      lastReconnectAttempt = now;

      if (reconnect()) {
        lastReconnectAttempt = 0;
      }
    }
  } else {
    Blynk.run();

    client.loop();

    t = dht.readTemperature();
    h = dht.readHumidity();
    rain = analogRead(rainpin);

    if (isnan(t) || isnan(t)) {
      Serial.println(F("Failed to read from DHT sensor!"));
      return;
    }

    if (rain < 300) {
      rainstatus = "VERY HEAVY RAIN";
    } else if (rain > 300 && rain <= 450) {
      rainstatus = "HEAVY RAIN";
    } else if (rain > 450 && rain <= 600) {
      rainstatus = "LIGHT RAIN";
    } else {
      rainstatus = "NO RAIN";
    }

    unsigned long currentMillis = millis();
    static unsigned long previousMillis = 0;
    const unsigned long interval = 2000;

    if (currentMillis - previousMillis >= interval) {
      previousMillis = currentMillis;

      snprintf(tempBuffer, sizeof(tempBuffer), "%.1f", t);
      snprintf(humBuffer, sizeof(humBuffer), "%.1f", h);
      strcpy(rainBuffer, rainstatus.c_str());

      if (client.publish("proj/temperature", tempBuffer)) {
        Serial.println("Temperature published successfully!");
      } else {
        Serial.println("Failed to publish temperature data!");
      }
      if (client.publish("proj/humidity", humBuffer)) {
        Serial.println("Humidity published successfully!");
      } else {
        Serial.println("Failed to publish humidity data!");
      }
      if (client.publish("proj/rain_status", rainBuffer)) {
        Serial.println("Rain status published successfully!");
      } else {
        Serial.println("Failed to publish rain status data!");
      }
    }

    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("Temp: ");
    lcd.print(t);
    lcd.print((char) 223);
    lcd.print("C");
    lcd.setCursor(0, 1);
    lcd.print("Humidity: ");
    lcd.print(h);
    lcd.print("%");
    delay(1000);
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("RAIN  STATUS");
    lcd.setCursor(0, 1);
    lcd.print(rainstatus);
    delay(1000);
  }
}

I am using the PubSubClient.h library for MQTT protocol and Blynk as my frontend. Despite subscribing to the topics and successfully publishing data (except for a few instances where data publication fails), my callback function is not triggered. However, the callback function must trigger so that I can receive the incoming message and write it on Blynk.