Question / Help Can't see a video clip

[divalasvegas]

Hi. I am live streaming for my fans on a Facebook page. I toggle between my webcam and Quicktime videos that live on my Mac. All but one of them shows up when I click on it. One of them only seems to output audio. When I click on Media Source to check it plays fine, but I cannot preview or livestream it. No video shows up, just the audio. Any ideas? Thanks in advance.