Administration - Installation - Core: Enable logging

hi Guys 

I'm running ilias 5.3.6.  I'm trying to setup User import.  However I am getting errors but my errors are not being written to the ilias.log file.  The path to my logfile  is /opt/iliasdata/ilias.log  group/owner www-data:www-data.


What do I need do to enable logging so I can see error messages?

I've attached the ilias.ini.php file.

Regards
Kevin