Ask the participants what browser (and version) they are using (all participants MUST use the latest version of Google Chrome)
Ask the participant to run a speed test (http://speedof.me/). Participants should have an internet connection with 10 mbps download and 10 mbps upload for best results. (Ethernet connection is preferred over Wifi).
Make sure participants have a connected webcam and audio source.
If you are using adblocker software, this may block browser access to your camera.