Orange light on charger, no other response

I have a 15" 2015 Macbook Pro that is giving me issues. It sat for about 6 months, I had another device that I was using in the mean time. I now want to use this one again, but I am not able to get it to boot. When I plug in a charger, the light goes from green to orange and then stays orange. I've left it on the charger for 24+ hours, and I'm still not getting any response.

I have a lot of repair experience, so I opened the device up. Right off the bat everything looks totally fine. I took the main board out to take a look at the back and everything in the computer, and nothing looks out of the ordinary. I have tried a handful of things to get the computer to boot. Unplugging battery and plugging it back in, as well as leaving the battery unplugged. I unplugged the trackpad, keyboard, ssd, airport card, etc, one-by-one and got no response. I then tried unplugging everything not required to boot the computer (with the exception of the screen and magsafe port), and still got no response out of it. I've also tried everything software wise, I don't even get a chime or any sign of booting so I'm not able to boot into safe mode / target disk mode / etc.

This is the dual graphics model of this computer. I know that it's common for the graphics chips to fail, but wouldn't the computer still boot even if the graphics chip is going out?

I do own a multi meter, but I don't have a lot of experience with using it on macbook pros. If anyone could provide me with some guidance on where to go from here that would be greatly appreciated!