Picture, but no sound

I have picture when watching a TV show, but no sound. This happened today when my wife was watching This is Us. The show started. There was sound during the intro, but when the show dialogue started there was no sound. Is it my broadband connection? I'm using Wifi. There is no ethernet connection available

Update: I just discovered that this problem doesn't happen on other shows. I switched to another TV show and everything works fine.