Learn CSS Flexbox by Building a Photo Gallery STEP 4- Step 4

HTML-CSS
#1

Tell us what’s happening:
Describe your issue in detail here.
I typed the code in the body paragraph but it is still saying Sorry, your code does not pass. I am not sure why

Your code so far

css flexbox photo gallery

Photo Gallery 
<!-- file: index.html -->
<!DOCTYPE html>
<html>
  <head lang="en">
    <h1>css flexbok photo gallery</h1>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Photo Gallery</title>
    <link rel="stylesheet" href="./styles.css">
  </head>
  <body>
    <div class="header"></div> 
    <body>
</html>

/* file: styles.css */

Your browser information:

User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/107.0.0.0 Safari/537.36

Challenge: Learn CSS Flexbox by Building a Photo Gallery - Step 4

Link to the challenge:

#2

this last tag should be </body> ?

#3

I added that but it is still not being accepted

#4

what does the hint say?