Thanks for the replies.
Yes, the audio track is checked off.
The clips are from Youtube and I can hear the audio when I watch them on Youtube.
Yes, when I view the audio mixer I can see the bar go up and down as though audio is trying to come out, but I can't hear anything.
I have no problem hearing the audio in WaveEditor.
My audio works for all other software except PD. It did work for PD until this morning.
I looked at everything recommended in that picture and it all looks good.
To provide some context, I was going back and forth between Sound Recorder when the problem hit. I was unplugging and re-plugging the headset into the computer. I think it might be a device/driver issue.