The same thing happened to mine but I replaced the screen myself since I have done multiple iPads Air, iPad 6th gen. The problem has to do with the FPC battery connector. When replacing a screen you usually isolate the battery so that you don’t accidentally damage the backlight or touch functionality when connecting the screen to the board. The problem with the newer iPads is that they are more fragile than the previous ones. They have small connectors and while sliding something under them to isolate the battery it’s easy to bend and break them. After replacing the screen on mine everything worked perfectly until I tried charging it and it wouldn’t go above 2-3%. I’m waiting for the replacement part to get here today.
I have one with the exact same problem that I found it seemed to be dead. What I did was unsolder the battery and connected a work bench dc power supply directly to the phone giving it 3.7volts the same as the battery. It turned on so I knew it wasn’t the iPod that was dead. The charger dock connection was bad so I replaced it. I supplied power using the dc power supply and plugged in my charger now it shows charging so the dock connector works. I tried connecting the battery but I think it’s dead because it doesn’t charge or anything. I’m waiting for battery I’ll post when I receive it to see if it finally comes back to life.