If you are using the setting show/remove posts that contain these words or phrases, otherwise known as the includewords/excludewords settings, you may be filtering out too many posts for the feed to display any. Instagram does not send posts from a specific user that also have a specific hashtag so the plugin will request all posts from the user account or hashtag feed and then will filter based on includword/excludeword. Here are some possible work arounds for this:
Using Permanent Feeds (version 2.9 and above)
1) Add the setting “permanent=true” to your shortcode
This will disable the feed’s ability to look for new posts and instead will create the feed from a permanent cache saved in the WordPress database.
2) Make your white list feed permanent in moderation mode
If you create a “white list” feed that never needs to be changed, you can save the white list as a “permanent” white list using the relevant setting while in Moderation Mode.
Note: If you make a feed “permanent” the plugin will attempt to gather enough posts to fill the feed when it’s first created. Even if no posts are retrieved initially, you can click the “load more” button until all posts that you were hoping to include in the feed are collected.
Using Other Settings
1) Raise the “Max concurrent API requests” setting
This setting will retrieve more posts initially to help with the filtering issue. Find it at the bottom of the “Customize” tab for Instagram Feed.