Vizio E422VA no sound (756TXBCB5K00903 Main Board)

[Pioneerx01]

This TV is perfectly working other than it has no sound. Main board in question is 756TXBCB5K00903.

There is no sound from any inputs.
I did complete TV reset to clear any previous settings.
Volume is up and not muted.
TV speakers are set to on.
No external speakers or headphones are connected.
I have applied 3V to the speakers, they are good.

I have tried using external speakers and headphones with no luck. When I use headphones, I made sure that TV speakers were off. I only hear slight white noise coming from headphones.

I have also noticed that the red SPDIF-out light on the main board is not on. With most TV's there is a red light coming from optical port, regardless if anything is connect to it or not.

I have zero experience in this type of issue, any ideas what I should check?

Thanks