Diane That issue occasionally comes up with my setup as well.
if you look at the lower right corner of your monitor you’ll see the speaker symbol. Click on that and see what the volume slider is set at. Sometimes for no apparent reason it slides back to a lower setting. Assuming your sound card is properly set increasing the volume on the slider does the trick. Mine is typically set between 30-40. Sometimes the simple things does the trick. Sometimes not. Hope this helps.
