The control script can show you the serial conversation if you turn debugging on and up in ZM. You could also uncomment all the logging stuff in the perl script - it shows the handshake as well.
Assuming your port is correct, your cable is ok, etc, etc...
You may not get any response from the camera until you reset it. You can do that by clicking the Reset button in the ZM control page on the Watch-mode window.
You could also issue the command "zmcontrol-ptel.pl reset" at a shell prompt (/usr/local/bin/zmcontrol-ptel.pl reset?).
As a last resort, try pressing the "Wake" button in the camera control window. It issues a reset and then a delayed power-on command. If those don't do it, you'll have to connect something up to the serial port with a null modem and see if anything is getting through.
If you have a Windoze box handy, I highly recommend testing your PictureTel and serial cable setup using a nice program called "BDLCAM"
BDLCAM let's you excercise the camera with (almost) no setup with regard to serial port. If BDLCAM can't move the camera, either the cable is no good, it needs a null-modem, or the serial logic/handshake and/or servos/encoders in the camera are ill.
And...BDLCAM web-serves and controls the camera quite nicely if you're in need of such a program for a Windows software base.