I added the below two lines to the cron config file (/etc/cron.d/librenms) and all works well now.
SHELL=/bin/bash
PATH=/opt/librenms:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
Fix found in Cron job for fast-ping (ping.php) don't work correct
Thanks for steering me in the right direction!