This request was working fine and returned MMM data for reporting. Unfortunately I'm not getting any error messages just being returned blank data set. I'm following the request example shown in this document https://developers.facebook.com/docs/marketing-api/insights/marketing-mix-modeling/
I have the same problem, but complementing it. When removing the breakdowns=mmm parameter the endpoint works, but it limits obtaining the fields country, device_platform, dma, platform_position, publisher_platform.
Can anyone help me?