You need to debug the agent , see the log : go to the hidden folder c:\programData\OCS Inventory NG\Agent\ and check all .log files. To have more verbose logs and understand better what happens set Debug=2 in your ocsinventory.ini and restart ocs service in the agent machine. Check also in the ocsinventory.ini that the http// server address is correctly set and that is reachable on your network. Try to force the communication in the systray clicking on "RUN OCS Inventory NG Agent Now".