Check your crontab file to make sure you have the appropriate discovery lines in place. I use:
*/5 * * * * librenms /opt/librenms/discovery.php -h new >> /dev/null 2>&1
33 */6 * * * librenms /opt/librenms/cronic /opt/librenms/discovery-wrapper.py 2
The first line (discovery.php -h new) runs every 5 minutes and only polls devices which are “new”, eg, devices you have added via the GUI but have not yet had any discovery run on them.
This is so any new devices you add will always have discovery run on them within 5 minutes.
The second line runs a full “rediscovery” (discovery of all existing devices) every 6 hours. This updates the more static properties of devices which are not updated during the 5 minute poller sessions.
This includes things like LLDP topology, make and model of devices etc.
When you say you are running the “command” manually, what command are you actually running ?