Problem with Mcp4261 and Arduino Mega2560

hello friends.
A few days ago I tried to run a mcp4261 with my arduino mega2560 without success.
I have made it work with my arduino uno but with my mega2560 I cannot.
I need your help.
I leave my code and schematic

I measure resistance between pins 6-7 and between 8-9

#include <SPI.h>


const int leftPot = B00010000; //   potenciometros pines bajos
const int rightPot = B00000000 ;  //potenciometro pines altos



const int slaveSelectPin  = 53; //pin 10 arduino uno - pin 53 arduino mega2560
const int shutdownPin = 7;



void setup() {
  // put your setup code here, to run once:

  Serial.begin(9600);
  Serial.println("inicio");

  pinMode (slaveSelectPin , OUTPUT);
  pinMode (shutdownPin, OUTPUT);

  SPI.begin ();

  digitalWrite(shutdownPin, LOW);
  delay(500);
  digitalWrite(shutdownPin, HIGH); //Turn off shutdown

  setPot(leftPot, 0);
  setPot(rightPot, 0);
}

void loop() {

  digitalWrite(shutdownPin, HIGH); //Turn off shutdown
  for (int i = 0; i < 255; i++) {


    setPot(leftPot, i);
    setPot(rightPot, i);
    delay(100);
    Serial.println(i);
  }

  for (int i = 255; i > 0; i--) {


    setPot(leftPot, i);
    setPot(rightPot, i);
    delay(100);
    Serial.println(i);
  }
}

void setPot(byte command, int potencia) {


  digitalWrite(slaveSelectPin, LOW);
  //B00010000   potenciometros pines bajos
  //B00000000   potenciometro pines altos
  SPI.transfer (command);

  SPI.transfer (potencia);

  digitalWrite(slaveSelectPin, HIGH);

}

I hope you can help my