Not seeing waiting room participant popup

It sometimes happens that I don't see the blue name pop up at the top of the screen when someone enters my waiting room, and I don't know they're there until I engage my mouse on the screen. This is a problem because I'm a Yoga teacher and am often not near my computer when facilitating meetings. Any idea why this is happening and what I can do to fix it? Could it have something to do with fact that my Macbook is on "do not disturb"?