my IR receiver received just UNKNOWN: 0 why?

#include <Arduino.h>

sender (pin3) code:
/*
   Define macros for input and output pin etc.

   #elif defined(__AVR__) // Default as for ATmega328 like on Uno, Nano etc.
  #define IR_RECEIVE_PIN      2 // To be compatible with interrupt example, pin 2 is chosen here.
  #define IR_SEND_PIN         3

*/
///// #include "PinDefinitionsAndMore.h"

///// #elif defined(__AVR__) // Default as for ATmega328 like on Uno, Nano etc.
#define IR_RECEIVE_PIN      2 // To be compatible with interrupt example, pin 2 is chosen here.
#define IR_SEND_PIN         3
#define TONE_PIN            4
#define APPLICATION_PIN     5
#define ALTERNATIVE_IR_FEEDBACK_LED_PIN 6 // E.g. used for examples which use LED_BUILDIN for example output.
#define _IR_TIMING_TEST_PIN  7

#include <IRremote.hpp>

#define DELAY_AFTER_SEND 2000
#define DELAY_AFTER_LOOP 5000

int button = 8;

void setup() {
  Serial.begin(115200);
  Serial.print("T_gd_setup!");

  Serial.print("File   : "), Serial.println(__FILE__);
  Serial.print("Date   : "), Serial.println(__DATE__);

  /*
     Print internal signal generation info
  */

  IrSender.enableIROut(38); // Call it with 38 kHz to initialize the values printed below
  /*
  Serial.print(F("Send signal mark duration is "));
  Serial.print(IrSender.periodOnTimeMicros);
  Serial.print(F(" us, pulse correction is "));
  Serial.print(IrSender.getPulseCorrectionNanos());
  Serial.print(F(" ns, total period is "));
  Serial.print(IrSender.periodTimeMicros);
  Serial.println(F(" us"));
*/
  pinMode(button, INPUT);

}

uint16_t sAddress = 0x0102; ////// A remote control that is programmed with device address 4E.24 can only control the digital signage display that is
                              /////// also programmed with device address 4E.24.
uint8_t sCommand = 0x34;    //// NEC command (HEX) 0x34 = Fast Backward, DEC 52,
uint8_t sRepeats = 0;

void loop() {
  /*
     Print values
  */
  /*
  Serial.println();
  Serial.print(F("address=0x"));
  Serial.print(sAddress, HEX);
  Serial.print(F(" command=0x"));
  Serial.print(sCommand, HEX);
  Serial.print(F(" repeats="));
  Serial.println(sRepeats);
  Serial.println();
  Serial.println();
  Serial.flush();
*/
  if (digitalRead(button) == HIGH) {

    Serial.println(F("Send NEC with 8 bit address"));
    Serial.flush();
    IrSender.sendNEC(sAddress & 0xFF, sCommand, sRepeats);
    delay(DELAY_AFTER_SEND); // delay must be greater than 5 ms (RECORD_GAP_MICROS), otherwise the receiver sees it as one long signal

    Serial.println(F("Send NEC with 16 bit address"));
    Serial.flush();
    IrSender.sendNEC(sAddress, sCommand, sRepeats);
    delay(DELAY_AFTER_SEND);
  }
}

#include <IRremote.h>

const int RECV_PIN = 2;

IRrecv irrecv(RECV_PIN);

decode_results results;

void setup()
{
  Serial.begin(9600);
  irrecv.enableIRIn(); // Start the receiver
  irrecv.blink13(true);

  Serial.print("File   : "), Serial.println(__FILE__);
  Serial.print("Date   : "), Serial.println(__DATE__);

}

void loop() {
  if (irrecv.decode()) {
    if (results.decode_type == NEC) {
      Serial.print("NEC: ");
    } else if (results.decode_type == SONY) {
      Serial.print("SONY: ");
    } else if (results.decode_type == RC5) {
      Serial.print("RC5: ");
    } else if (results.decode_type == RC6) {
      Serial.print("RC6: ");
    } else if (results.decode_type == UNKNOWN) {
      Serial.print("UNKNOWN: ");
    }
    Serial.println(results.value, HEX);
    irrecv.resume(); // Receive the next value
  }
}