If you trust the power supply board you purchased, then the main board should be receiving power to turn on the Main board.
That main board then turns on the power light and the TV's logic board. Then that logic board turns on the Ysus and Xsus boards that light up the plasma panel. You should hear a buzz/hum coming from the plasma panel at that time, and see the panel go from pitch black to a gently lit gray color, then the picture appears after that. All plasma TVs follow that start up procedure.
I don't know if you have Tech Skills or a voltmeter, but LG Techs use this procedure to verify the power supply board.
Yeah, try finding 100 Watt bulbs and sockets to wire in series for that Vs test...not as easy since they did away with 100 Watt bulbs.
Overall...you tested the remote and the pushbuttons. You've replaced the power supply. You still don't get that power on light on the front of the TV, so that indicates the main board can't turn on the power on light. That has to happen next, THEN the power supply turns on and fires up the logic board which finally fires up the Ysustain and Xsustain boards.
It's a process of elimination.
You can disconnect the sustain boards from the new power supply and simply measure the VS voltage pins to GND pins on those boards, see if the resistance increases up to 2000 ohms within a minute. I'd trust those boards to NOT BLOW the main power supply board then.
Watch that video...maybe a couple times to see what that tech does. Then get back with me, letting me know if you have a voltmeter for testing, ok?