I have found that the Tokbox video + voice chat used on Roll20 works best in Firefox, works okay in Chrome and doesn't work at all in Internet Explorer.
Disable Video + Voice: Go to my settings. Under Video + Voice, "For I want to Broadcast to others" select Disable, for "I want to Receive from others"select Disable. For Video/Player Avatar Size select Small.
Renable Video + VoiceGo to my settings. Under Video + Voice, "For I want to Broadcast to others" select Voice Only, for "I want to Receive from others" select Voice Only. Doing this should change the Tokbox window from profile picture to Toxbox flash player window.
Tokbox Device Setup: Click the wrench icon to access the settings for Tokbox. Verify that your webcam and/or sound device are correct, if not select Change and choose the correct device. If your camera is working you will see your webcam transmitting video. If your microphone is working you will see the audio levels fluctuate when speaking. When done click the x in the upper right corner. *If either of these does not work go back to your computers hardware settings and verify that they are working. Use the computers internal diagnotics to test the devices.
Flashplayer Security: Flashplayer requires a certain level of security to access your camera. Verify the Toxbox applet has permission to run. Right click on the Tokbox applet and select "Global Settings...". Click the second tab Camera and Mic. Verify that "Ask me when a site wants to use camera or microphone (recommended) is selected. Click the "Camera and Microphone Settings by Site..." button. Scroll down and find the website "static.tokbox.com". Verify it has the Allow access to your Camera and Mic. If not, click the website and select Allow in the drop down menu below.
I have found that when I am first launching the campaign I have to disable and renable the video and voice upon starting a session. If you continue to have problems it is either a hardware issue or flashplayer rights issue. Hope this helps.