Device is not showing graphs

Hi team,
I’ve recently implemented LibreNMS but I’m still getting errors on graphs (showing errors) and I cannot also change the hostname (no DNS) but I want the description to show instead of the hostname. PLEASE HELP this is urgent guys.
Please see the attachments.
Thanks in advance.

First please validate your install post the output.

Second check here ->
https://docs.librenms.org/#Support/FAQ/#faq10