AD 5675R I2C cannot write/update a constant value like 1 V

Hello all,

I am working on AD5675R with an Arduino Uno (no evaluation board). I can locate the address of this chip in Arduino as 12, but I cannot write a value to any channel (digital multimeter shows 0 V for all channels all the time). 
Inline image 1
All I want to do is: output a constant DC value from DAC channel 0. But using this code, channel 0 (or any other channel) always output 0. My example code is:
#include <Wire.h>
 byte addr = 12;
 byte DAC0_addr = 30;
 uint16_t output0 = 30000; // expecting an output voltage value of 30000/65535 volt
  void setup() 
  void loop() 
   Wire.beginTransmission(addr);// transmit data to slave decive
   Wire.write(DAC0_addr); //30=0011 0000 write and update DAC channel 0 
   Wire.write( (output0 >> 8) & 0xFF); // write high 
   Wire.write( (output0) & 0xFF); // write low
Please help!!