Hoping to help someone…
On librenms I ran poller.php -h {device} -m ports -d
This showed the graphite command being sent.
On the graphite server I ran tcpdump port 2003 -vvv -w graphite.pcap
This gave me the packets that were arriving to the server destined for graphite process
In the packets, I searched for the plain text command that libre sent and found it. This meant the issue had to be with graphite.
Found /etc/carbon/carbon.conf and a log section. Turn it on and found errors like ‘Error tagging carbon.agents.ts’ and ‘Error requesting "http://{server ip}/’
I had to update ‘GRAPHITE_URL’ in carbon.conf and all the missing data started coming in