Trying to use '<?php include' to call some content

Hello, This is possible beyond your scope of support. I want to call in the footer and header content on a site i am working on on this page:
https://birdclick.co.uk/endonet/the-endonet-team.html
I can't see why this is working for me. I'm probably doing something wrong! Can you see my error? Here is the code I am using to call the the header content:
<header id="header" class="no-sticky">
<div id="header-wrap">
<?php include 'include/header.php';?>
</div>
<div class="header-wrap-clone"></div>
</header>

Many thanks

Rob

I have got an example to work here https://birdclick.co.uk/endonet/workingexample.php
When I change the extension to .php for the page I where i want to call the header.php it stops working.

I'm not even sure how but this is no longer an issue. I worked backwards from the example file replacing code bit by bit and solved it! Close this ticket please