We will probably need to see your code before we can help you. Be sure to wrap it in triple back ticks (three back ticks on a line by itself, then paste your code underneath, then on a separate line below your code three more triple back ticks).
You’ve actually done everything right. The error you are getting about a self-closing tag is a bug. While many people do end self-closing tags with /> it is not a requirement in HTML and the test should pass with just >.
So to pass this test you just need to end the <link> tag with /> in order to appease the tests. By the way, I actually opened an issue on this a while ago and it looks like there is a pull request (#45890) in the works to fix it.
OK, after a few hours of sleep I noticed that I forgot to put an “s” on “style.css”. Should have been “styles.css” . Now it will pass if I close it with “/>”