Trying to control dc motors in L293D motor shield for Arduino

[Fefes]

I am trying to control 4 dc motors for a car using L293D motor shield for Arduino Uno.I have some experience with Labview,but I am new with Arduino coding and LINX.I am trying to make 4 buttons(forward,backward,right,left) that when held on,the car will move accordingly.Because I am not sure how to use Digital Write N chan (since I want to have 4 commands),I tried using Digital Write 1 Channel and tried testing with only 1 button,but it didn't work out.I dont know if there is an issue with my Arduino Code,the blocks I am using on Labview or both.Below I show the block diagram and the Arduino code.

#include <AFMotor.h>

AF_DCMotor motor1(1);  // Front-left motor
AF_DCMotor motor2(2);  // Front-right motor
AF_DCMotor motor3(3);  // Back-left motor
AF_DCMotor motor4(4);  // Back-right motor

void setup() {
  Serial.begin(9600);  // Set the baud rate to match LabVIEW
  motor1.setSpeed(255);
  motor2.setSpeed(255);
  motor3.setSpeed(255);
  motor4.setSpeed(255);

  motor1.run(RELEASE);
  motor2.run(RELEASE);
  motor3.run(RELEASE);
  motor4.run(RELEASE);
}

void loop() {
  if (Serial.available() > 0) {
    char command = Serial.read();

    switch (command) {
      case 'F':
        moveForward();
        break;
      case 'B':
        moveBackward();
        break;
      case 'L':
        moveLeft();
        break;
      case 'R':
        moveRight();
        break;
      case 'S':  // Stop command
        stopMotors();
        break;
      default:
        stopMotors();  // Default to stopping if an unknown command is received
        break;
    }
  }
}

void moveForward() {
  motor1.run(FORWARD);
  motor2.run(FORWARD);
  motor3.run(FORWARD);
  motor4.run(FORWARD);
}

void moveBackward() {
  motor1.run(BACKWARD);
  motor2.run(BACKWARD);
  motor3.run(BACKWARD);
  motor4.run(BACKWARD);
}

void moveRight() {
  motor1.run(BACKWARD);
  motor2.run(FORWARD);
  motor3.run(FORWARD);
  motor4.run(BACKWARD);
}

void moveLeft() {
  motor1.run(FORWARD);
  motor2.run(BACKWARD);
  motor3.run(BACKWARD);
  motor4.run(FORWARD);
}

void stopMotors() {
  motor1.run(RELEASE);
  motor2.run(RELEASE);
  motor3.run(RELEASE);
  motor4.run(RELEASE);
}