Hi kamailio'ns

I am working on Kamailio V 4.0.3, installed from Ubuntu 12.04(precise) repository.
My SIP clients(jitsi) are registering to kamailio sever successfully but their presence is not sharing between the clients. 
I am frequently logging following presence related errors in syslog while trying to register SIP clients to kamailio server:

Oct 25 20:01:05 kamailio /usr/sbin/kamailio[15274]: INFO: pua_usrloc [ul_publish.c:221]: ul_publish(): not marked for publish
Oct 25 20:01:05 kamailio /usr/sbin/kamailio[15273]: WARNING: presence [publish.c:481]: handle_publish(): Missing or unsupported event header field value
Oct 25 20:01:05 kamailio /usr/sbin/kamailio[15273]: ERROR: presence [publish.c:484]: handle_publish():     event=[reg]


what could be the wrong ?
How can i reslove this issue ?

please find in the attachment is my kamailio config file. (suggest me if any changes to be made to this configuration)

Any help will greatly appreciate.

Regards,
Ravi