I seem to have lost sound for instant chat messages and I can't figure out how to fix it.

The site used to make a "dwoop" noise when I received an instant message, somewhat like a water drop.  Now nothing.

I have tried on both Chrome and Edge.  Also rechecked all my account notification settings.

A person I chat with says he still gets sounds for instant messages, so this is obviously something wrong on my end.

Does Tom or anyone reading this know how I can fix this?