Can no longer hear audio on videos

Can anyone help with the below issue please?

We have a weekly webinar where we play a demo video (which has been downloaded to whoever's laptop) to a wider audience. All of a sudden, a few weeks ago - participants could no longer hear the audio when the video was being played. Everything worked fine before so it's really confusing - we were able to quickly find a solution and screen share to play the video from our Google Drive instead of the downloaded version. This is becoming an inconvenience so we'd love to fix the issue. I haven't been able to find anything this specific on the help articles.

The video is being played from a few colleagues' devices and we all have MacOS Ventura laptops.

Thank you!