Recently, I have lost the audio when I open a video in Photoshop CC. I don't think it is a problem with the video file, because I have tried it on videos that have played with audio before, and the videos play with sound in other apps. I've checked to make sure that both audio buttons are active, both the one near the play button at the top of the timeline palette as well as the icon on the audio track. The one near the play button is active, but it turns grey as soon as I press play (see attached images). I suspect some setting has been changed, since the files that once worked no longer work, and the lack of audio was not associated with an update of Photoshop or my operating system.
This is how the panel looks before playback:
This is what happens as soon as I press play:
Problem solved, the system volume for Photoshop had been turned down, but due to a problem with the mixer panel it wasn't visible. I solved the problem by right clicking on the speaker icon on the taskbar and selecting the "Open Volume Mixer" option. The mixer looked like this:
At some point, the volume for Photoshop must have been turned down to zero, but I couldn't see this because the slider was not visible. I increased the volume by putting the cursor in the Photoshop section of the mixer and adjusting the volume with the scroll wheel on my mouse.