finally solve it:
Install the missing module perl SOAP :: Transport :: HTTP
edit the files z-ocsinventory-server.conf
the lisguientes lines:
PerlSetEnv OCS_DB_USER ocs
# Password for user
PerlSetVar OCS_DB_PWD "password"
<Location / ocsinterface>
require user "SOAP_USER"
and edit also this:
the following line
define ( "PSWD_BASE", "password");
Given that in both cases the password is the password that you place your ocs user in the database.
Once this is done run the following commands:
sudo a2ensite z-ocsinventory-server.conf
service apache2 reload
With that and the server and agents have been reported :)