Hope the screenshot is clear:

Control Panel Sounds: not working-soundsnotplaying.jpg

In fact the window seems unfamiliar; shouldn't it have check boxes showing which actions have been set?

If it's relevant this is Version 1903 (OS Build 18362.418)

- - - Updated - - -

OK, sorted thanks. I found a suggestion to update the driver for the 'High Definition Audio Device'. That got my 'Program Events' sounds back.

As for my other query, I now remember that the speaker icon indicates the enabled events.