Please first check the following:
- do you have Alpine Instagram Plugin installed? The proper plugin can be found in Recommended plugins directory or downloaded from: https://wordpress.org/plugins/alpine-photo-tile-for-instagram/
- once the plugin is installed, is the plugin connected with your instagram account? You can connect in the plugin's settings (Add User)
- is the username added properly in theme's options? It has to be entered exactly as it is (case sensitive). So if your instagram username is instagramuser, do not enter it like INSTAGRAMUSER or Instagramuser.