XML Style error and RSS button is inactive

Two issues: first when I stick this widget into a sidebar, the RSS button isn’t “active” or “clickable,” even though I’ve checked the option in the Settings page

Second: when you click on the category I get a dump of the XML and the error message: “This XML file does not appear to have any style information associated with it.”

https://ww.wp.xz.cn/plugins/category-specific-rss-feed-menu/