HTTP Response Code Plesk

[Pappasalt]

We have a rule in our .htaccess file that works well, it looks like this:
RewriteRule ^status/400$ - [R=400,NC,L]
However, when we attempt to display a custom error using http_response_code(400), it doesn't work as expected. Instead, it displays a message saying "This page isn’t working".
Could someone kindly assist with this issue?