CSS file not being linked even though the route is correct

So I have a HTML,CSS and php project for uni.
While working, I have faced a problem where a <link> code in a file called headerHome.php,that includes the navbar which I include in each file, is not linking to the CSS file(called index.css).

here is the code for reference as well as my files layout :

HeaderHome.php:

.
.
.
<!doctype html>
<html lang="en">
  <head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <title>Score'em</title>
    <link rel="stylesheet" href="CSS/index.css">
    <link href="https://cdn.jsdelivr.net/npm/[email protected]/dist/css/bootstrap.min.css" rel="stylesheet" >
    <script src="https://cdn.jsdelivr.net/npm/@popperjs/[email protected]/dist/umd/popper.min.js" ></script>
    <script src="https://cdn.jsdelivr.net/npm/[email protected]/dist/js/bootstrap.min.js" integrity="sha384-Atwg2Pkwv9vp0ygtn1JAojH0nYbwNJLPhwyoVbhoPwBhjQPR5VtM2+xf0Uwh9KtT" crossorigin="anonymous"></script>
</body>
  </head>
.
.

profile.php(the file in question) :

<?php include("includes/headerHome.php");
$user = FetchUserInfo($_SESSION['User']);
?>

<div class="ContainerProfile">
<a href="#"  id="uploadImage">
    <img id="CircleImage" height="128" width="128" src="images/logo.png" alt="Cloud Chen">
</a>
</div>

<?php include("includes/footer.php");?>

The CSS Code :

#uploadImage {
    color: transparent; 
    font-weight: normal;
    text-decoration: none;
  }
  

#CircleImage{
    border-radius: 50%;
}

.ContainerProfile{
    background-color: #44b8f6;
}

Files Layout

Output

Can someone please explain to me what I did wrong ?