One of my friends had an issue like this, muttered something about having to "whitelist opentok.net" for Flash, did something to his computer, and got it working. Perhaps you should check your Flash settings.
Tony: Hello
Argh! Giant Ant!
Brett (GM): Hello?
Tony: Hello
Brett (GM): Looking for video chat....
Tony: Not sure
Brett (GM): try your cogwheel at top right
check that you have selected to receive and transmitt voice and video
Tony: I've got mine set to video and voice
Yep, got both of those one
on
Do you need to assign characters?
I remember the intro video saying something about the video chat, but I cannot recall what it was...
Raov Toeja: Now I am in Character!
Brett (GM): yes
I hoped it might kick off the chat if you were playing, like, a character
Okay, I turned my broadcast off and then on again
got a popup asking me for permission to start Flash
and now I have a moving picture of myself in lower left
Raov Toeja: That is a good start \
Tony: I'm not getting anything here yet....
Brett (GM): try turning off receive and turning it back on again
Nothing?
Tony: OK, I just had to whitelist roll20.net for Flash
Just a sec
need to whitelist opentok.net