If the stylus doesn't appear to be working, one possibility that it may be plugged into the Ethernet port instead of the stylus port.
The stylus will plug into the Ethernet port and "click" into place, so it appears that this is the correct location for the connection.
Simply re-connect the stylus to the correct port and check for functionality again.
Below is an image showing the stylus port on the left and Ethernet port on the right as if you are looking at the ports from the back side of the zSpace. The Ethernet port is the port closer to the edge of the display.