This is specifically about hashtags using the Facebook Instagram API.
Has anyone successfully retrieved the thumbnail url for a video in a hashtag feed? Even when using the graph API I cannot get anything to return?
To get the thumbnail_url you have to make an extra call to the Oembed endpoint using the post for the video and an access token. You must have an approved APP for this to work also. https://developers.facebook.com/docs/instagram/oembed/
Then you will see the thumbnail_url option available to you.