I let the battery drain last night before plugging it back in. It wouldn’t turn on though, so I ended up unplugging the battery and plugging it back in to kick it into boot. I also flashed the BIOS again earlier and nothing. I can keep unplugging the battery to kick it into boot whenever it shuts off, but opening it up everytime I want to turn it on is far from ideal lol.

I’m suspecting it’s a physical failure of the Power button now. I’ve seen one person suggest shifting the Mobo up a bit because it can shift down to where the button can’t reach after extended use, so I may try that next. I’m also going to unplug the battery and clean the physical button with Alcohol to hopefully improve contact.