There is a headphones volume setting in the TV menu, which is used to adjust the headphones volume independent of the volume control for the TV loudspeaker.
If the headphones volume is set to minimum, you will not be able to hear sound from the headphones.
To adjust the headphones volume, do the following:
When you have set the headphones volume to an audible level and there is still no sound from the headphones, try the headphones on another device.