Vizio e600i-B3 no power, even with new power supply and main board

I have a Vizio e600i-B3 that won't power on. The standby light does not turn on either. The power supply has 12v standby as well as 3v PS-ON. Pushing the power button doesn't change anything. I've tried replacing the power supply with no success, and even got a new main board to replace, but having the same problem. Where do I proceed from here?