Xfce and system sound issue

There appears to be an issue when I run Linux Mint on Xfce. Audio is present and works ok if I run an application like VLC or SMPlayer, but there is an issue with sound events. Eg, if I bring up the Sound Settings GUI and click on 'Test Sound' nothing is heard. But if I run command speaker-test -c2 -t wav then I get sound that the GUI should have given me ('Front Left, Front Right'....). Similarly if if I bring up the Sound Settings GUI, and hit the tab 'Sounds', none of the events listed work. I know that libcanberra has to be installed for sound events to work, and running command dpkg -l | grep canberra produces output as below, so nothing looks to be missing there.

Code:ii gnome-session-canberra 0.30-5ubuntu1 amd64 GNOME session log in and log out sound events
ii libcanberra-gtk3-0:amd64 0.30-5ubuntu1 amd64 GTK+ 3.0 helper for playing widget event sounds with libcanberra
ii libcanberra-gtk3-module:amd64 0.30-5ubuntu1 amd64 translates GTK3 widgets signals to event sounds
ii libcanberra-pulse:amd64 0.30-5ubuntu1 amd64 PulseAudio backend for libcanberra
ii libcanberra0:amd64 0.30-5ubuntu1 amd64 simple abstract interface for playing event soundsThe same output shows when I run Mint on Cinnamon where the sound events all work just fine. I've checked that nothing has been muted. So what is the problem with Xfce?