I'm also having the same problem of notifications not sounding. I'm also on Mac. It's a recent development. I've double checked volume, notification settings at the mac level, and notification settings at the webex level several times.
I started having this problem within the last week and a half or two. What versions are people running? I'm on macOS Catalina 10.15.7 with Webex App version 18.104.22.16829.
I just did some research on internal cases. To help folks out - it seems that there are specific affected versions of the Webex App, specifically including (but not limited to) 22.214.171.12416 and 126.96.36.19929.
There is a current known bug for this issue, CSCvy18132. This issue should be fixed in June via Webex version 41.6 and later. Hopefully that helps!
Ok, last update for now. I just downloaded the latest version of the Webex app here: https://www.webex.com/downloads.html/ After installing, this brought me up to version 188.8.131.5287, which actually fixes the issue for me! If you all are struggling, try manually downloading the latest version and see if that fixes your issue.
It seems that fixed the issue for me as well. Odd because I uninstalled/reinstalled just last week.
Either this v41.5 was just released or I somehow got an older version. Thank you Zachary for coming back to update us!