I have been struggling with this forever and couldn't figure out why it was so intermittent. I finally figured out why on my system it was happening. I use multiple screens and will stream while I work. While working I sometimes need to create a video of my screen so I'll pause the streaming, and open up Camtasia to record my screen. If any screen recording software is open all the streaming services will only show black screen with audio. Make sure you have any software that records your screen is closed out. For me that is Snagit, Camtasia, Vidyard, ect.