LG 65 C3 PUA won't turn on.

Hello everyone, I'm trying to determine how to figure out what is the problem with the tv I have. It is a 65C3PUA and it no longer turns on. When I press the power button the red light flashes but doesn't turn white. The other day it would turn white when pressing the power button but now it no longer does that. Just wondering if this would be a power board or main board problem and how to know which one it is? Depending on which one I would order a part to try and fix it, of course the tv is just outside of warranty.