Jason. This link is the standard Webex advice on sharing and settings.
https://help.webex.com/en-us/article/nkjrl9eb/Share-motion-and-video-content-in-Webex-Meetings-and-Webex-Webinars
On the other hand, I have the same problem, and these settings didn't help.
Are you set as Host for the meeting when you try to share? I've found sometimes when I'm Host it works, if I'm co-host it doesn't. But it's erratic for me. I don't know the real answer yet.
