RFID reader Hz-1050

I am using a HZ-1050 RFID reader with my Arduino

https://www.elabpeers.com/hz-1050-rfid-em-id.html

First of all i used the Serial port one to get the tag readings. using this code

int i;
void setup()
{
Serial.begin(9600); // start serial to PC 
Serial1.begin(9600);
pinMode(13,OUTPUT);
}
void loop()
{
 if (Serial1.available())
 { 
   while(Serial1.available()){
      i = Serial1.read();}
   Serial.print(i);
 }
}

Which worked fine and i got readings,
Then i tried with the software serial and made correct connections and used this code to get readings

#include <SoftwareSerial.h>

String i;
SoftwareSerial rfid (4,5);

void setup()
{
Serial.begin(9600); 
rfid.begin(9600);
pinMode(13,OUTPUT);
}
void loop()
{
 if (rfid.available())
 { 
   while(rfid.available())
   {
      i = rfid.readString();
    }
   Serial.print(i);
 }
}

But this didn’t give me any readings what can be the reason,Please help