Yes, it is working for me now.
Sorry, I was trying to implement this in the splash screen for the "Basic Viewer" configurable web app at first, rather than in Web AppBuilder. In the configurable web app, the video displays in the splash screen text editor, but reverts to displaying the html code when you save and launch the app. I just assumed they would function the same. Bummer, because I prefer the look and style of the basic viewer configurable web app.
Thanks for your help!