Facebook Ads API Insights: Not receiving `dda_results` in Ads Insights API response

I am using the Facebook Ads API to pull Ads Insights data for my campaigns. I am trying to include dda_results in the data I fetch, which according to the Facebook documentation should contain "Estimated incremental conversions caused by a given ad".

Here’s the API query I am using:

https://graph.facebook.com/v18.0/act_XXXX/insights?level=ad&fields=campaign_name,campaign_id,adset_name,adset_id,ad_name,ad_id,clicks,reach,impressions,objective,spend,inline_link_clicks,dda_results&limit=500&time_increment=1&access_token=XXXX&time_range[since]=2023-09-10&time_range[until]=2023-09-21

The API returns the other fields I have requested (like campaign_name, adset_name, etc.) but dda_results comes up empty.

What I have checked:

• DDA is enabled for the campaigns
• The access token has necessary permissions
• The campaign objectives should support DDA data

Why am I not receiving any data in dda_results, and how can I resolve this issue?

I executed the above API query expecting to receive dda_results as part of the JSON response, along with the other fields like campaign_name and adset_name. While I successfully received data for all the other specified fields, the dda_results field came up empty in the response. I expected dda_results to contain estimated incremental conversions as per the Facebook documentation.

I have verified that DDA is enabled for my campaigns, my access token has the necessary permissions, and my campaign objectives should be compatible with DDA data. Despite this, I’m not receiving any data in the dda_results field.