SPI read write for 32bits data

I changed to this...but still not working...

#include <SPI.h>

int CS = 10;


union FourByte{
    struct {
      unsigned long value:24; //24bit register values go in here
      byte command:8; //8bit command goes in here.
    };
    byte bit8[4]; //this is just used for efficient conversion of the above into 4 bytes.
};

void setup(){
  SPI.begin();
  SPI.setBitOrder(MSBFIRST);
  SPI.setDataMode(SPI_MODE0);
  
  Serial.begin(9600);
  pinMode(CS, OUTPUT);
  digitalWrite(CS, HIGH);
  //Page
  //example of reading data
 // unsigned long voltage = SPI_read(0x04);//Instantaneous Voltage Channel 1
  
  //example of writing data
  union FourByte INI;
  INI.command = 0b11111111; //Write to config register
  INI.value = 0xFFFFFE; //This is the default value from datasheet, just using it as an example.
  SPI_write(INI);
  
  
  union FourByte data;
  data.command = 0b11101000; //Write to config register
  data.value = 0xFFFFFE; //This is the default value from datasheet, just using it as an example.
  SPI_write(data);
}

void loop(){
  unsigned long voltage = SPI_read(0x04);
  Serial.print("Voltage=");
  Serial.println(voltage); 
  delay(1000); 
}

void SPI_write(union FourByte data) {
  digitalWrite(CS,LOW); //Using CS pin, so sync1/sync0 bytes not needed
  for(char i = 3; i >= 0; i--){
    SPI.transfer(data.bit8[i]); //transfer all 4 bytes of data - command first, then Big Endian transfer of the 24bit value.
  }
  digitalWrite(CS,HIGH);
}

unsigned long SPI_read(byte command){
  digitalWrite(CS,LOW); //SS goes low to mark start of transmission
  union FourByte data = {0xFEFEFE,command}; //generate the data to be sent, i.e. your command plus the Sync bytes.
  for(char i = 3; i >= 0; i--){
    data.bit8[i] = SPI.transfer(data.bit8[i]); //send the data whilst reading in the result
  }
  digitalWrite(CS,HIGH); //SS goes high to mark end of transmission
  return data.value; //return the 24bit value recieved.
}