Regarding AD5761 DAC

Hi.
I've connected the AD5761
For the programming of the AD5761, I did the following steps:
- write to control_reg <= X"0400DE";// output range =0 to 15V
I load the input dac register with X"ffffff" data to get 15V on Vout
The Vout is always 0V, the signals seem to me correct.

what is the problem