Cant change the background image with CSS

I'm just trying to change my background image on my website. I can change the background color but not the image. This is my first timeusing php so I don't know if I should know something there. Just been using HTML/CSS/JS. Appreciate the help!

style.css

body{
        font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
        background-image: url("/img/indexbackground.png");
}

index.php:

 <!DOCTYPE html>
    <html lang="en">
    <head>
        <meta charset="UTF-8">
        <meta http-equiv="X-UA-Compatible" content="IE=edge">
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
        <title>Quickbuy</title>
        <link rel="stylesheet" href="css/reset.css">
        <link rel="stylesheet" href="css/style.css">
    </head>

Solution

The issue is that you didn't put your CSS inside of a style tag.

You also didn't include </html>. That doesn't affect this issue, however it may cause issues with more complex webpages and older browsers.

Here is the updated code, in a snippet:

<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Quickbuy</title>
  <link rel="stylesheet" href="css/reset.css">
  <link rel="stylesheet" href="css/style.css">
  <style>
    body {
      font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
      background-image: url("/img/indexbackground.png");
      background-color: #22d; /*Background color is being used to replace background image, remove it in your code.*/
    }
  </style>
</head>

</html>

CSS can't just be like this

element {
  color: red;
}
<!DOCTYPE html>
...

It must be in a style tag.

<!DOCTYPE html>
<html>
<head>
  <style>
    element {
      color: red;
    }
  </style>
</head>
<body>
...
</body>
</html>