I'm not sure. I'm embedding the svgs as per html standards (in an img tag). I'm not sure why it's not displaying the hover.
Discussion
It's using embedded CSS for the hover, so something in the page's CSS might be overriding it, I don't know much about it myself, just experimenting.
text:hover {
fill: orange;
}
It turns out CSS interactions won’t work if the img tag is used. Will work if directly inside an SVG tag or iframe. Neither are great solutions.