My bad. The correct path is {VCO_INSTALLATION_FOLDER}\app-server\server\vmo\conf\log4j.xml
I assume you are using vCO installed on Windows. log4j.xml file must already exist. The important information will be logged in server.log file.
I see that attached app-server\server\vmo\log\server.log file is quite small ussualy it will contain much more info.