What version of Videopad is being used? Try this one... For licensed users upgrades are free for up to six months from purchase date. After that, VP will continue to fully function but a fee will be required in order to register the newest. Retain your old install file and registration info.
Right-click the speaker icon at the bottom-right of the Windows screen 
and open the volume mixer.
With Videopad running, confirm that the VP slider is up, and not muted. 
This will display differently on Windows 8/10, but the idea is the same. Also be sure that the volume slider to the left of the VP audio track isn't turned down, or the track muted.