If you are using a private tracker, you might need to go to Tools > Manage Cookies and add your site’s credentials for the feed to work. If you'd like to dive deeper, let me know: Are you using a private tracker that requires a login? How to auto download torrent via rss
By default, the RSS Reader tab might be hidden in your qBittorrent interface. Open . Look at the top menu bar and click on View . add rss feed to qbittorrent