Some users of Plays.tv get no sound or audio in their recordings. If you are in this group, do you use a USB headset called the Razer Kraken Chroma 7.1? Or perhaps you use another headset that uses 7.1 audio?
If you do, there's a temporary way to get around this problem:
Go into Task Manager by hitting Ctrl-Alt-Delete, then choose Task Manager.
In the Processes tab, find a process called Kraken71ChromaHelper.exe *32. (It may have a slightly different name.)
Click the End Process button. Now when you start a game recording, you should get audio back.