Audio cuts out after spotlighting

Hi, I hope you can help. I've been using Zoom for teaching online classes since lockdown without any issues. Recently I've been having issues with participants losing audio after I spotlight myself - they can hear me but I can no longer hear them. Their audio was fine before I'd spotlighted myself. How can I resolve this? Or what advice can I give my students to help them resolve it at their end.

I'm on Mac OS15.6.1 with the latest version of Zoom (v6.5.12)

Thanks for your help & advice.