Sound goes mute after a few minutes

I bought this app so that I could talk to my parents on their brand new MacBook Pro. Since they already had Facetime installed, I bought the app to use on my MacBook Pro that didnt come with it. It works for a couple of minutes then they stop hearing audio from me. I can hear them, but they cant hear me. It happened every time we tried it. They are so upset about it they want to return their MacBook Pro that they just bought.

fridapainter about FaceTime, v1.0.2