Hi Marie,
Check your wires and any switches that the cats could step on and turn off. My cats turn off my speakers all the time cause it has a push button on top.

Check your sound settings something some programs will mute the sound and don't reset it back to your settings. Click on the little speaker icon and move the bar up if it is all the way down.

Other things to check may be too complicated like the device manager....you could look in there and see if you see any yellow exclamation points.

Eva