If the alarm does not sound on Android 10, check the following.

Confirmation within the Shift Work Calendar app

Settings > Version
1.8.0-192 or later version

Shift pattern list > Open the corresponding shift
The alarm is set to a scheduled shift time other than “None”.

Settings > Shift Alarm Type
Alarm is turned on

Check Android OS settings

Settings app > Apps & notifications > App info > Shift Work Calendar > Notifications > Shift alarm

"Alerting" is ON

"Pop on screen" is ON

If the silent mode is ON, it will not sound, so turn it off.

If you want to sound even in silent mode,

Settings app > Apps and notifications > App info > Shift Work Calendar > Notifications> Shift alarm

Please turn on "Override Do Not Disturb"

Depending on your model, even the above settings may not sound.

In that case, use it as a notification instead of an alarm.

Settings > Shift Alarm Type
change to notification