Why won’t my Switch Lite turn on after a shell swap?

Hello, I recently swapped out the old yellow shell of my Switch Lite for a new one. Now it won’t turn on, the screen is completely black, not a hint of light. It worked fine before. No water damage. I let it charge overnight but it still wouldn’t work. I stowed it away for later and when I pulled it out again the backside was warm. I repeated the power cycling options. Still no joy. Things that I have tried to do to fix it:

1. Took it all apart and put it back together again to make sure every connection was snug
2. Held down the power button for 20 seconds and then pressed the power button again.
3. Reset my OEM charger.

I followed all the instructions from Erica Griffen’s YouTube video, even removing and re-applying the thermal paste. I’ve built PCs from scratch so I thought I could do this but I guess I was wrong. I don’t know how to do any other diagnostic evaluations. I’m wondering how I can tell if it’s a battery, MB or an LCD issue? Thanks in advance for any help you can provide.