Usually the only thing you can do is unplug everything you can from the mainboard (in this case probably just the flash and the ram), turn it on and see if it lights up. If it doesn’t, then it must be the mainboard as it’s all that’s left, so it’s game over.
ps when you have the lid off make sure the switch is actually being pressed, some S-class I’ve seen the button doesn’t reach the switch (not seen this on a V, but you never know).
I pulled the flash chip from the unit and the power indicators started working! I replaced the flash chip with one from a known good system and the problem reappeared. I then realized that the flash chip had been seated incorrectly and was misaligned by a set of pins. I put the original flash back into the unit correctly and it works!