[Observium] graphs

Hi,

We are using Observium SE

Version Information *Observium* 17.11.8960 (29th November 2017) *OS* Linux 2.6.32-696.16.1.el6.x86_64 [amd64] (CentOS 6.9) *Apache* 2.2.15 (CentOS) *PHP* 7.0.24 (OPcache: ENABLED) *Python* 2.6.6 *MySQL* 5.1.73 (extension: mysqli 5.1.73) *SNMP* NET-SNMP 5.5 *RRDtool* 1.6.0

We have a server (Mysql+rrd+apache) and 419 devices monitored, but not showas the graphs, it says NAN. There any reason for this?

Cron job is setup

# Run multithreaded poller wrapper every 5 minutes */5 * * * * root /opt/observium/poller-wrapper.py >> /dev/null 2>&1