[Observium] observium distributed

We are configuring and testing observium distributed.... it works fine !, but when i add a new device on web interface i must check skip ICMP echo checks. if not i get a message Could not ping X.X.X.X

in observium main config.php is installed fping 3-10 $config['fping'] = "usr/local/sbin/fping";

in poller too is installed fping 3-10 $config['fping'] = "usr/local/sbin/fping";