Can you please try taking the steps in our Audio Visual Trouble Shooting guide. If none of those resolve your issue please try following Steps 1-3 of our Solving Technical Issues guide, taking special care to temporarily disable all browser add-ons and extensions, temporarily pause your anti-virus, and try switching browsers (for Chrome/Firefox specific issues) to see if one of those components is causing the problem. If all of that fails, please follow Step 4 , including providing all of the necessary information, so that we can further assist you.