Today we repaired a PS4 pro that had no power via the power button but beeped 3 times when pressing the eject button.
This usually leads to a faulty Southbridge IC

We removed the faulty southbridge and replaced it with a reballed one from a donor board.

Once we reballed the replacement and removed the defective IC from the motherboard,it was ready to reflow back onto the board.

Replacing the Southbridge has repaired the fault this PS4 had and brought it back to life

It just goes to show that a no power issue or not turning on problem is not always related to the power supply. The southbridge is kind of a system control chip and it tells the console to turn on and turn other components on in a sequence.