Here is my code to the external CSS file. It was able to render my JavaScript but not my CSS.
<!DOCTYPE html>
<html lang="en">
<head>
<title>React App</title>
<link rel="stylesheet" href="../src/styles.css" type="text/css" />
</head>
<body>
<div id="root"></div>
<script src="../src/index.js" type="text/jsx"></script>
</body>
</html>
Simply put
<head>
<title>React App</title>
<link rel="stylesheet" href="./styles.css" type="text/css" />
</head>
OR
<head>
<title>React App</title>
<link rel="stylesheet" href="styles.css" type="text/css" />
</head>