Audio failure

When trying to play a score, the cursor moves over the score at normal speed, but no sound is played. Turn on the mixer and the individual volumes show 0 (the computer volume synthesizer is not muted). Dragging the slider, the volume remains at 0. The metronome has no sound. There is also no sound when entering notes and when selecting notes. In short, everything is fine except that I can't hear the sound. I have tried restarting the computer and reinstalling the software but to no avail.

Suggestions would be appreciated.