AD9172 PRODID register Reading error

Register  "0x004" and "0x005"   are linked with PRODID low byte and high byte.   In the datasheet, the default  are  0x72 and 0x91。However, the registers are all "0" ,as shown in below pictures:

We have checked and made sure that there are no problems with our SPI reading programme.

So could you please help figure out the reason for this reading error?

Thank you &Regards,

Vicky