Looks like https://www.hinz.org.nz/resource/rss/news.rss replies to GET requests with a 301 to https://cdn.ymaws.com/www.hinz.org.nz/resource/rss/news.rss but to HEAD requests with a 403.
You can configure the plugin to download the feed from https://cdn.ymaws.com/www.hinz.org.nz/resource/rss/news.rss directly to avoid their mess.