Instagram sections do not return any photos when choosing photos by hastag.
As of Nov 17, 2015 Instagram introduced Sandbox mode. When you authenticate your site with Instagram you create a client (your site) and authorize this client to communicate with Instagram on your behalf. This client is automatically put in Sandbox mode - which is kind of a testing environment. In this testing environment your client only has access to photos that you or your sandbox users have posted on Instagram - but you do not have access to the general archive of Instagram photos. This does not have any effect when you are displaying your latest Instagram photos - but when you display photos by a certain tag you should be aware that only images added by you or your sandbox users with that particular tag will be displayed - not photos with that same tag from the general Instagram archive. This could mean that you will get a very limited amount of photos to display (sometimes none). To increase the number of available photos you should either add more sandbox users or switch your client from Sandbox mode to live mode. For more information visit this link: https://www.instagram.com/developer/sandbox/