Hi there!
Well, I hope that you used the eval-board-circuit and all the information given in the datasheet concerning
* single-ended clocking,
* analog-output-filter
* correct voltages ...and so on. I cant see it on your sreenshot.
To answer your question, you have to give some more information,
since that dds-IC will not do anything, if you don't programm it.
One thing I see, is that you left "OSK"-input open. It's CMOS-input, don't let it open!
the same: "ext_pwr_down". It's CMOS-input. don't let it open!
The "OSK"-pin can (if you programmed it that way) just pull your amplitude to zero.
The "ext_pwr_down" can cause unpredicable behaviour.
If that doesnt help, maybe you can add some information about the registers.
Have fun! Matzekowski