If you are sharing a post from your Instagram account to your Facebook page and the image is not being included then it may be because you’re sharing the post from the Instagram website at instagram.com rather than from the mobile app. Sharing a post via instagram.com unfortunately doesn’t allow the image to come through in Facebook’s API. It’s marked as a “status” post by Facebook and so doesn’t include the image, which is why you’ll see only the text displayed. In order to include the image and have it shared as a “photo” post on Facebook you’d need to share it using the Instagram app.
To share a post via the app you would first need to link your Instagram account to your Facebook Page by following these directions, and then once it’s linked you can share a post by doing the following:
1) Click on the post in your feed
2) Click the 3 dots in the top right of the post
3) Select “Share”
4) Make sure “Facebook” is enabled and then click “Share” in the top right