Verify:
1. Verify that User module of Net Control 2 (Net Control 2 Server) was properly installed on USER computer:
Net Control 2 icon should be present in the System Notification Area (System Tray, area beside system clock):
 

Solution:
When icon is not present in the System Notification Area, most likely, User module of Net Control 2 was not properly installed on user computers. You need to install the software on each User computer, which you wish to control.

Installing software, be sure that user components are selected for installation: