PC specs? CPU/GPU/Ram.
Right-click in the area to the left of the audio track and confirm that it isn't shown as muted 
Try this next. Close Videopad. Using Windows Explorer (file manager), delete all files in these folders...
"C:\Program Files (x86)\NCH Software\Components"
"C:\Users\<account name>\AppData\Roaming\NCH Software\Components"
Now reinstall Videopad.