Figured it out. So, it appears that Oxidized hates to be pointed at any IP other than 127.0.0.1. I had to set the Oxidized REST IP to 127.0.0.1:8888 and the Oxidized source http url to http://127.0.0.1/api/v0/oxidized in the Oxidized config. I also had to change config.php for LibreNMS to point at 127.0.0.1:8888 in the Oxidized stanza. Previously I had these set to the network interface that I am pointing the LibreNMS web site to via nginx.