Jsut so I understand this, Neflix is an app from the Sony? If this is the case, you haven't connected audio from the Sony to your receiver. When using Neftlix, your Sony display becomes an audio source and that needs to get routed to the AVR. Connect one more HDMI cable from the display to HDMI3 to get the sound. If that doesn't work, use either the coax audio out from the display to (AV2 input) or optical out (AV1 input) on the AVR.