Macbook A1342 Won't Power On

Hello all, apologies if this thread already exists somewhere but I couldn't find it for this exact model so I'm posting it.

I do IT for a school district in my city, I am the Senior technician for all the campuses and one of my jobs is overseeing inventory, repairing (full range), and image management for all of the school's MacBooks. There's a MacBook I'm working on that has confounded me a bit. This is a late 2009-early 2010 MacBook A1342 Unibody model... A student submitted the laptop saying that it wouldn't power on so I started with the basics: Is it a bad charger? A bad battery? Did a related internal component become disconnected or fried somehow?

1) First I changed chargers with one I use all the time and know for a fact that works fine. The charger light goes solid green and the connection is solid - laptop is completely unresponsive when pressing the power button. No fan noise, no lights, no display activity, no nothing at all. The entire device is completely unresponsive.

2) Secondly, I opened the MacBook and ensured that the battery connection was good. It was, but I went ahead and reseated the connection. This made no difference as I suspected so I went ahead and totally removed the battery and tried powering the machine on using only the AC power adapter. This also did not work... I then placed a brand new fully charged battery inside the machine and tried to power on using only battery power but this also did not work.

3) At this point, I'm thinking the problem is either the MagSafe Board, the Logic board itself, or the keyconnector for the power button is bad. So I start with the next order of business which is replacing the MagSafe board. I carefully removed the logic board from the lower case and replaced the MagSafe Board with a brand new one. This also did not work.... NOTE: I did go back and triple check that all connections to the logic board were connected and in place, nothing was forgotten.

4) I decide to reseat the connector to the logic board that makes the power button work, as well as looked for any noticeable damage to the connector. It looked fine and I verified it was connected all the way and secured when reseating it. This made no difference and the machine still will not power on. Again, no lights, no fan movement, no display activity, no nothing. The machine is still totally dead and totally unresponsive.

5) I decide that it's a bad logic/motherboard... So, I pull one from another identical MacBook model that powers on fine and swap it out. After the replacement is complete and all components properly secured, the device still will not power on...

NOTE: I have double checked all of my methods of replacement using ifixit step by step. I also build and decommission machines from the ground up all the time and have done it for a living for years. I'm very very confident that everything was replaced properly, all components reconnected correctly, and nothing was forgotten.

Ssoooo, at this point, I can only suspect that the actual connector for the power button is bad, which is attached to the lower unibody case wiring, however it seems odd for something like that to just go bad all of the sudden and there are actual multiple machines that are doing this same thing. I'm confident that I have done all of the forementioned repairs correctly and that I didn't miss anything, however actually new to the world of Mac and I'm not discounting the possibility that there is something else I can try before purchasing a piece of equipment that could possibly not make a difference.

Any help and farther insight into this problem would be very appreciated. Thank you!