The link "extended monitoring" on the admin settings panel "tips&tricks" points to https://docs.nextcloud.com/server/13/go.php?to=admin-monitoring and is redirected to https://docs.nextcloud.com/server/13/admin_manual/operations/considerations_on_monitoring.html.
Your server says "file not found" when clicking on the link.
The link "extended monitoring" on the admin settings panel "tips&tricks" points to https://docs.nextcloud.com/server/13/go.php?to=admin-monitoring and is redirected to https://docs.nextcloud.com/server/13/admin_manual/operations/considerations_on_monitoring.html.
Your server says "file not found" when clicking on the link.