If your video is playing, but you cannot hear the audio track, here are a few troubleshooting suggestions.

First, check the volume on your device. Typically the volume controls are along the bottom of your screen. This placement varies depending your computer. 

You may also have a external speaker attached to your computer. Check to see that your speaker is on and the volume is up.

Now check the volume on the video inside the program. You can do that by hovering over the video screen with your cursor to bring up the menu bar (shown below). Next to the video time, there is an audio icon. Click the audio icon and make sure the sound is turned up. If all the bars are highlighted, your volume is turned up. 

If you have checked all of the above, and are still having issues, please contact support for further assistance.