DIAGNOSIS HDMI-CEC/ARC handshake failure. This is a common issue with all brands, often triggered by a TV software update or power state change.
FIX Power off everything. Disconnect the HDMI cable from both the TV and soundbar. Reconnect it firmly. Power on the TV first, let it fully load. Then power on the soundbar. Go to TV settings, find HDMI-CEC or Simplink (LG)/Bravia Sync (Sony), turn it OFF, wait 10 seconds, then turn it ON again.
IF THAT DIDN'T WORK On the soundbar, change the Digital Audio Input format. Press the 'Source' button to select HDMI, then hold the 'Sound Mode' button on the remote for 3 seconds to cycle formats. Try 'PCM' or 'Auto'.
HEADS UP Some older or budget TVs have buggy HDMI-CEC implementation. You may need to use the optical audio input instead for reliable TV audio, losing TV remote volume control.