Cannot, no matter how hard i try, connect either of my two adc v720w cameras via wifi, they are fine connected with lan cable, bought them used. what am i missing here?
There is some added difficulty in diagnosing a used camera, but in this case the primary thing to check is whether or not the Wifi antenna is installed and tightened down properly. The 720W uses a removable external wifi antenna that screws into the back of the unit. This was possibly removed in order to ship the unit. Can you double check that both are attached and screwed down?
thank you Jason, unfortunately, i am an RF engineer for a living 
checked them. I picked them up directly from the end user also. having said that, when i tell the camera to ’ discover’ the wifi, the rear led goes red and then it times out.
Not a problem, always have to check the physical issues first.
Have you tried WPS to connect?
Do you have your 2.4 Ghz network hidden for any reason?
It may be necessary to factory default the cams as a next step. The reset button is the same as the WPS button. Hold the button down for 15-20 seconds until the LED flashes red and green. Any luck after?