UPDATE: The API now supports this, and so does Intagrate! https://intagrate.io/docs/multiple-images-videos/
Recently Instagram announced that you could now share up to 10 photos as one post on Instagram, as a type of gallery. Unfortunately at the time of writing, there is no support for these galleries via the API. The API response for a multi-image post contains the first image only, and the media type is still set as ‘image’.
The Instagram Developer blog has been silent since June last year, so it doesn’t look like this feature is being ported to the API anytime soon. This means that the Intagrate plugin can’t display these images on your WordPress site 🙁