I recently changed from Ubuntu 18.04 to Ubuntu 20.04 and overall I'm very pleased with 20.04, however one odd thing I've since experienced is that Slack (desktop version) does not successfully play the typing-like sound when a message is received. The icon on the top right still has the circle turn red.
If I play a YouTube video I hear it well so I know my speakers are working.
In Settings under Sound, then Alert Sound if I choose different sounds these work:
In Settings under Notifications, then Slack, I have Notifications and Sound Alerts turned on:
Within Slack itself it seems I have things set correctly:
On this last screen if I press Show an Example or change the setting under the Notification sound drop-down I am able to hear the different sounds from within Slack, but they still don't play when a message arrives.
This may sound like a trial matter, however it's caused me to not respond to some urgent messages when working from home recently and therefore is a significant concern. Unfortunately I don't always notice the small circle in the top right corner turning red if I'm really into what I'm doing.
I've tried uninstalling and reinstalling Slack, no change. I never had this problem with Ubuntu 18.04.
Has anybody else had this happen or is there anything else I should check?
I had exactly the same problem on Manjaro and finally solved it. Are you using an HDMI audio device?
On my system, it seems when audio starts playing to my HDMI monitor, it takes a half second or so for the device to wake up and start playing. I'm not really sure what causes it, but apparently all the Slack sounds are so short that the sound finishes before the device wakes up.
The tests all seemed to work though - I was usually doing the tests just after a notification sound failed to play, so the device was already awake at that point. It seems to stay awake for a few minutes before suspending again.
I finally realized that if I play music on this device (which I never do since the HDMI speakers are terrible), that the Slack sounds work because the device is already awake.
My "fix" was to switch to a different set of speakers plugged into the analog audio output, now Slack sounds work fine. If you're stuck on HDMI audio, maybe playing some inaudible noise will keep the sound device up?