Firstly, press the volume UP button on your remote control to make sure your SoundBox is not on mute. Increase the volume to check if any audio is heard.
While watching TV, if there is a blue LED seen on my SoundBox, it means that your SoundBox is paired with a device through Bluetooth.
Press the blue button on your remote to change the sound mode to TV.
If you are using a Bluetooth device, firstly make sure, a blue LED is seen on your SoundBox.
If no blue LED is seen, press the blue button on your remote control to change the sound mode to Bluetooth.
Check if your device is paired to the SoundBox by navigating to 'Settings' -> 'Sound' -> 'Bluetooth pairing'.