Sharing Audio and Video

I am a fitness instructor zooming my class. I have a mixer board and typically, I change the speakers to USB Codec, I share my screen first with Basic, selecting Share Sound and Optimize for Video Clip at the bottom, then I go into Advanced and Share computer audio and it works great - my class can hear my voice and the music I am playing from iTunes through the computer. This morning when I tried it, every time I hit Computer Audio in Advanced, the other two buttons at the bottom (Share Sound and Optimize for Video Clip) would come off, and the class could not hear me well and could not hear the music at all. Has anyone experienced this? Any fix for it? I had to cancel my class this morning.