Hi, thanks for the heads up, I've just upgraded my SDS.
I've tested only my ESP SW, though it communicates exactly same like your implementation.
It still works without any problems, no additional AWG verifications were introduced
I'm attaching sample sweep output from a diy 40db attenuator.
If look your image it looks weird. Exept it tell your AWG is working with Siglent what was perhaps main thing.
But then, your setup and settings are possible totally mess.
What signal goes to reference channel (Ch1)
First make sure your signal source (AWG) output go to your DUT (in your case your selfmade attenuator) input and exactly same signal goes to Ch1 (as long as you have not defined other channel for reference).
Then your DUT (device under test - your attenuator) output goes to Ch2 (because in your image you have selected it (or it is just as scope default).
First it need be sure these signal connections are ok.
Then need look about your BodePlot II settings are right if need.
Basic signal connections (user can free select channels including what is ref channel)
You have measured attenuator but your display show "40 - 60dB" amplifier.
In attached image Ch4 is selected for DUT out but scope factory default is Ch2
(Ch4 is selected for main DUT out in image related to other things = with 1 in 1 out system can keep 1GHz samplerate but also Ch4 is far from Ch1 so it may crosstalk with strong reference signal bit less than Ch2 if need get all out from dynamic range = in basic works just forget this and happy use Ch1 Ch2 pair)