Can't read RFID tag

Excuse me, I am trying to use RFID reader #28140 to read tags but I’ve made the right connection of the arduino board to the reader. It shows nothing on the serial monitor. Can someone do me a favor?

Here is my code

const int StartByte=10;
const int StopByte=13;
const int tagLength=10;
const int enable=7;
const int led=13;
char tag[tagLength+1];
int index=0;

void setup() 
{
  Serial.begin(2400);
  pinMode(enable,OUTPUT);
  digitalWrite(enable,LOW);
  pinMode(led,OUTPUT);
}

void loop() 
{
  if (Serial.available()>tagLength)
  {
    digitalWrite(led,HIGH);
    delay(1000);
    digitalWrite(led,LOW);
    delay(1000);
    if(Serial.read()==StartByte)
    {
      index=0;
      while(index<tagLength)
      {
         tag[index]=Serial.read();
         index++;
      }
      if(Serial.read()==StopByte)
      {
        tag[index]=0;
        Serial.print("RFID tag is:  ");
        Serial.println(tag);   
      }
    }
    
  }
}

Start with a simple sketch to see if your assumptions about the data stream are correct:

void setup(){
    Serial.begin(2400);
    pinMode(7,OUTPUT);
    digitalWrite(7,LOW);
}

void loop() {
    int c = Serial.read();
    if (c != -1) Serial.write((char)c);
}

Be sure to set Serial Monitor to 2400 baud. Everything you type into Serial Monitor should echo back. Anything you receive from your RFID module should show up on Serial Monitor.