That's so odd...
Mind if I ask about your install process as well as the notification you got when it did the update? Correct me if I'm wrong, but Descendant doesn't have the update thing in the settings and not sure about a built-in updater, but I know you can check for updates through it's "What's New" app.
Everything works through my testing without a problem.
The DND button they're talking about appear when you increase your DPI. If you go into your developer options and set your own DPI, it first pops up around 450-455 if I remember right. It'll be a little moon icon above your volume slider.