We are using version 2.3 of the FB graph API to get insights (specifically viral impressions, reach, engaged, talking about, and impressions) for a page photo post. It works without issue. However when we try to make this same call in version 2.4, it fails. See an example call we used in the Graph API explorer below
/1129724967054634_1214739968553133/insights/?metric=['post_impressions_unique']
We've tried both PageID_ObjectID and PageID_Photo ID in the call, but neither returns the insights data mentioned above. We can get likes and comments for the Object, but nothing at all for the Photo. Are we missing some change in the way Facebook treats page photo posts between versions?