Usually this comes from a browser problem:
- Check that you are using version 52 of chrome.
- Exit and restart Chrome
- Check with your IT department that the RTMP protocol is authorized.
- Check if screencast extension "screen capturing" is activated: To do this type in the "chrome: // extensions" url bar and delete the old extension
- Check that your webcam is activated (webcam logo not barred on the right side of the URL bar)