L298N motor driver not working with Arduino UNO R3

I was trying to use the motor driver, but the motors aren't spinning for some reason.

I am sure the motors are working; I tried and tested them. I can't understand if there is a problem with the code, motor driver or the Arduino board.

Arduino board used: Arduino UNO R3

Here is the code:

char data;  //Serial

void setup() {
  // put your setup code here, to run once:
  pinMode(4, OUTPUT);
  pinMode(5, OUTPUT);
  pinMode(6, OUTPUT);
  pinMode(7, OUTPUT);

  Serial.begin(9600);
}

void loop() {
  // put your main code here, to run repeatedly:
  if (Serial.available()) {
    data = Serial.read();
    Serial.println(data);
  }

  if (data == '1') {
    digitalWrite(4,HIGH);
    digitalWrite(5,LOW);
    digitalWrite(6,HIGH);
    digitalWrite(7,LOW);
  }
}