user59950: 
This is the relay board
I am using nodemcu to make a home automation project which is controlled by google assistant. This is the code i am using is this one
#include <ESP8266WiFi.h>
#include "Adafruit_MQTT.h"
#include "Adafruit_MQTT_Client.h"

#define Relay1            D0
#define Relay2            D1
#define Relay3            D2
#define Relay4            D3

#define WLAN_SSID       "Subhodip"             // Your SSID
#define WLAN_PASS       "09003244135"        // Your password

/************************* Adafruit.io Setup *********************************/

#define AIO_SERVER      "io.adafruit.com"
#define AIO_SERVERPORT  1883                   // use 8883 for SSL
#define AIO_USERNAME    "SubhodipRoy"            // Replace it with your username
#define AIO_KEY         "50a98bb44f6b48b69e645badadf8fb577894"   // Replace with your Project Auth Key

/************ Global State (you don't need to change this!) ******************/

// Create an ESP8266 WiFiClient class to connect to the MQTT server.
WiFiClient client;
// or... use WiFiFlientSecure for SSL
//WiFiClientSecure client;

// Setup the MQTT client class by passing in the WiFi client and MQTT server and login details.
Adafruit_MQTT_Client mqtt(&client, AIO_SERVER, AIO_SERVERPORT, AIO_USERNAME, AIO_KEY);

/****************************** Feeds ***************************************/

// Setup a feed called 'onoff' for subscribing to changes.
Adafruit_MQTT_Subscribe Light1 = Adafruit_MQTT_Subscribe(&mqtt, AIO_USERNAME"/feeds/Relay1"); // FeedName
Adafruit_MQTT_Subscribe Light2 = Adafruit_MQTT_Subscribe(&mqtt, AIO_USERNAME "/feeds/Relay2");
Adafruit_MQTT_Subscribe Light3 = Adafruit_MQTT_Subscribe(&mqtt, AIO_USERNAME "/feeds/Relay3");
Adafruit_MQTT_Subscribe Light4 = Adafruit_MQTT_Subscribe(&mqtt, AIO_USERNAME "/feeds/Relay4");

void MQTT_connect();

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

  pinMode(Relay1, OUTPUT);
  pinMode(Relay2, OUTPUT);
  pinMode(Relay3, OUTPUT);
  pinMode(Relay4, OUTPUT);

  // Connect to WiFi access point.
  Serial.println(); Serial.println();
  Serial.print("Connecting to ");
  Serial.println(WLAN_SSID);

  WiFi.begin(WLAN_SSID, WLAN_PASS);
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println();

  Serial.println("WiFi connected");
  Serial.println("IP address: "); 
  Serial.println(WiFi.localIP());


  // Setup MQTT subscription for onoff feed.
  mqtt.subscribe(&Light1);
  mqtt.subscribe(&Light3);
  mqtt.subscribe(&Light2);
  mqtt.subscribe(&Light4);
}

void loop() {

  MQTT_connect();

  Adafruit_MQTT_Subscribe *subscription;
  while ((subscription = mqtt.readSubscription(20000))) {
    if (subscription == &Light1) {
      Serial.print(F("Got: "));
      Serial.println((char *)Light1.lastread);
      int Light1_State = atoi((char *)Light1.lastread);
      digitalWrite(Relay1, Light1_State);

    }
    if (subscription == &Light2) {
      Serial.print(F("Got: "));
      Serial.println((char *)Light2.lastread);
      int Light2_State = atoi((char *)Light2.lastread);
      digitalWrite(Relay2, Light2_State);
    }
    if (subscription == &Light3) {
      Serial.print(F("Got: "));
      Serial.println((char *)Light3.lastread);
      int Light3_State = atoi((char *)Light3.lastread);
      digitalWrite(Relay3, Light3_State);
    }
    if (subscription == &Light4) {
      Serial.print(F("Got: "));
      Serial.println((char *)Light4.lastread);
      int Light4_State = atoi((char *)Light4.lastread);
      digitalWrite(Relay4, Light4_State);

    }
  }


}

void MQTT_connect() {
  int8_t ret;

  // Stop if already connected.
  if (mqtt.connected()) {
    return;
  }

  Serial.print("Connecting to MQTT... ");

  uint8_t retries = 3;

  while ((ret = mqtt.connect()) != 0) { // connect will return 0 for connected
    Serial.println(mqtt.connectErrorString(ret));
    Serial.println("Retrying MQTT connection in 5 seconds...");
    mqtt.disconnect();
    delay(5000);  // wait 5 seconds
    retries--;
    if (retries == 0) {
      // basically die and wait for WDT to reset me
      while (1);
    }
  }
  Serial.println("MQTT Connected!");

}

Connecting the pins as stated below
VIN-->VCC
D0--> IN1
D1--> IN2
D2-->IN3
D3-->IN4
Gnd-->Gnd
But only IN2,IN3 and IN4 led of relay board are only glowing the IN1 is not glowing and the relays are not switching on/off... 
Anyone please help....
Please give any solution... Why the relays are not switch-on?
Please reply as soon as possible... I am very disturbed... Even cant sleep at night....

user58962: From the description and comments it looks like the problem is HW related. I recommend you to do a relay module test (wthout NodeMCU): 

Try to switch the relays on/off  just by connecting the power source you are using for powering the NodeMCU. Connect VCC–5V, GND–GND and one of the IN channels directly to 5V pin. If the relay switches on, try another channel. If not, try to connect IN to GND instead of 5V (inverted logic).
If 1. did not worked, check the yellow jumper on the right side of the relay board. The jumper must be attached (in case you don't want to use another independent power source just for relays).
If 2. did not worked, check if the relay board is not intended for use with 12 V DC power source (check the relay marking).

At this point you should know if all channels of the relay module are working and also the switching logic (inverted/noninverted). The next step should be connecting the relay module to the NodeMCU and run a "blink" example for all channels. If all is working well, we will be sure the problem is NOT HW related...

59950: <p><img src="https://i.stack.imgur.com/ObKcZ.jpg" alt="enter image description here"></p>

<p>This is the relay board</p>

<p>I am using nodemcu to make a home automation project which is controlled by google assistant. This is the code i am using is this one</p>

<pre><code>#include &lt;ESP8266WiFi.h&gt;
#include "Adafruit_MQTT.h"
#include "Adafruit_MQTT_Client.h"

#define Relay1            D0
#define Relay2            D1
#define Relay3            D2
#define Relay4            D3

#define WLAN_SSID       "Subhodip"             // Your SSID
#define WLAN_PASS       "09003244135"        // Your password

/************************* Adafruit.io Setup *********************************/

#define AIO_SERVER      "io.adafruit.com"
#define AIO_SERVERPORT  1883                   // use 8883 for SSL
#define AIO_USERNAME    "SubhodipRoy"            // Replace it with your username
#define AIO_KEY         "50a98bb44f6b48b69e645badadf8fb577894"   // Replace with your Project Auth Key

/************ Global State (you don't need to change this!) ******************/

// Create an ESP8266 WiFiClient class to connect to the MQTT server.
WiFiClient client;
// or... use WiFiFlientSecure for SSL
//WiFiClientSecure client;

// Setup the MQTT client class by passing in the WiFi client and MQTT server and login details.
Adafruit_MQTT_Client mqtt(&amp;client, AIO_SERVER, AIO_SERVERPORT, AIO_USERNAME, AIO_KEY);

/****************************** Feeds ***************************************/

// Setup a feed called 'onoff' for subscribing to changes.
Adafruit_MQTT_Subscribe Light1 = Adafruit_MQTT_Subscribe(&amp;mqtt, AIO_USERNAME"/feeds/Relay1"); // FeedName
Adafruit_MQTT_Subscribe Light2 = Adafruit_MQTT_Subscribe(&amp;mqtt, AIO_USERNAME "/feeds/Relay2");
Adafruit_MQTT_Subscribe Light3 = Adafruit_MQTT_Subscribe(&amp;mqtt, AIO_USERNAME "/feeds/Relay3");
Adafruit_MQTT_Subscribe Light4 = Adafruit_MQTT_Subscribe(&amp;mqtt, AIO_USERNAME "/feeds/Relay4");

void MQTT_connect();

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

  pinMode(Relay1, OUTPUT);
  pinMode(Relay2, OUTPUT);
  pinMode(Relay3, OUTPUT);
  pinMode(Relay4, OUTPUT);

  // Connect to WiFi access point.
  Serial.println(); Serial.println();
  Serial.print("Connecting to ");
  Serial.println(WLAN_SSID);

  WiFi.begin(WLAN_SSID, WLAN_PASS);
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println();

  Serial.println("WiFi connected");
  Serial.println("IP address: "); 
  Serial.println(WiFi.localIP());


  // Setup MQTT subscription for onoff feed.
  mqtt.subscribe(&amp;Light1);
  mqtt.subscribe(&amp;Light3);
  mqtt.subscribe(&amp;Light2);
  mqtt.subscribe(&amp;Light4);
}

void loop() {

  MQTT_connect();

  Adafruit_MQTT_Subscribe *subscription;
  while ((subscription = mqtt.readSubscription(20000))) {
    if (subscription == &amp;Light1) {
      Serial.print(F("Got: "));
      Serial.println((char *)Light1.lastread);
      int Light1_State = atoi((char *)Light1.lastread);
      digitalWrite(Relay1, Light1_State);

    }
    if (subscription == &amp;Light2) {
      Serial.print(F("Got: "));
      Serial.println((char *)Light2.lastread);
      int Light2_State = atoi((char *)Light2.lastread);
      digitalWrite(Relay2, Light2_State);
    }
    if (subscription == &amp;Light3) {
      Serial.print(F("Got: "));
      Serial.println((char *)Light3.lastread);
      int Light3_State = atoi((char *)Light3.lastread);
      digitalWrite(Relay3, Light3_State);
    }
    if (subscription == &amp;Light4) {
      Serial.print(F("Got: "));
      Serial.println((char *)Light4.lastread);
      int Light4_State = atoi((char *)Light4.lastread);
      digitalWrite(Relay4, Light4_State);

    }
  }


}

void MQTT_connect() {
  int8_t ret;

  // Stop if already connected.
  if (mqtt.connected()) {
    return;
  }

  Serial.print("Connecting to MQTT... ");

  uint8_t retries = 3;

  while ((ret = mqtt.connect()) != 0) { // connect will return 0 for connected
    Serial.println(mqtt.connectErrorString(ret));
    Serial.println("Retrying MQTT connection in 5 seconds...");
    mqtt.disconnect();
    delay(5000);  // wait 5 seconds
    retries--;
    if (retries == 0) {
      // basically die and wait for WDT to reset me
      while (1);
    }
  }
  Serial.println("MQTT Connected!");

}
</code></pre>

<p>Connecting the pins as stated below</p>

<p>VIN-->VCC
D0--> IN1
D1--> IN2
D2-->IN3
D3-->IN4
Gnd-->Gnd</p>

<p>But only IN2,IN3 and IN4 led of relay board are only glowing the IN1 is not glowing and the relays are not switching on/off... </p>

<p>Anyone please help....</p>

<p>Please give any solution... Why the relays are not switch-on?</p>

<p>Please reply as soon as possible... I am very disturbed... Even cant sleep at night....</p>
 58962: <p>From the description and comments it looks like the problem is HW related. I recommend you to do a relay module test (wthout NodeMCU): </p>

<ol>
<li>Try to switch the relays on/off  just by connecting the power source you are using for powering the NodeMCU. Connect VCC–5V, GND–GND and one of the IN channels directly to 5V pin. If the relay switches on, try another channel. If not, try to connect IN to GND instead of 5V (inverted logic).</li>
<li>If 1. did not worked, check the yellow jumper on the right side of the relay board. The jumper must be attached (in case you don't want to use another independent power source just for relays).</li>
<li>If 2. did not worked, check if the relay board is not intended for use with 12 V DC power source (check the relay marking).</li>
</ol>

<p>At this point you should know if all channels of the relay module are working and also the switching logic (inverted/noninverted). The next step should be connecting the relay module to the NodeMCU and run a "blink" example for all channels. If all is working well, we will be sure the problem is NOT HW related...</p>
