Hi Peter,

Thx for your answer and its check-list... which helped me to find my mistake and to  solve the problem

when you run the agent manually on the affected server, does it return an
output
/usr/lib/observium_agent/local/apache
<<<apache>>>
56775

No.

If not, do you use vhosts ?

Yes

B-) but I had not enabled the default site. As soon as I did, things worked perfectly

Date: Fri, 24 Jun 2016 08:50:20 +1000
From: Peter.Hine@familycourt.gov.au
To: Observium Network Observation System <observium@observium.org>
Subject: Re: [Observium] One of my Apache servers do not show
        [SEC=UNCLASSIFIED]
when you run the agent manually on the affected server, does it return an
output
/usr/lib/observium_agent/local/apache
<<<apache>>>
56775
[...]
>>>
If not, do you use vhosts ?
does mod_security.conf need updating to allow access from localhost.
do you get a perl error on LWP:Simple ?



thanks