Header not showing

Does anyone know why this could happen?

This definitely depends on your theme’s settings.

Can you give an example of a page where the header is not appearing? I viewed several pages on your site, but couldn’t find any instance.

When you say you couldnt find any instances, did they all have the header or dont have?

Yes, all the pages I tested had the header. Even utility pages (eg search, 404, cart, checkout, etc), and archives pages (category, tag, date, etc) all had the same header.

That’s why I asked to see an example of a page where the header is NOT appearing.

If this is only happening when you’re logged in, you could have some code that’s set up to only show the header when logged in or if you’re an admin.

This is the is_admin() function documentation:
https://developer.ww.wp.xz.cn/reference/functions/is_admin/

This is the is_user_logged_in() function:
https://developer.ww.wp.xz.cn/reference/functions/is_user_logged_in/

You could check both functions.php and header.php to see if either of those functions exist, and whether they are related to displaying the header of the page.