iPad Air 2 Dead After Screen Reconnection

Hey everyone, hoping someone can help me figure this out.

What happened:

• I replaced the screen on my iPad Air 2. It was on 7% battery at the time.
• I disconnected the screen without disconnecting the battery (biggets mistake).
• When I reconnected the screen, nothing happened—no display, no signs of life.
• I reconnected the old cracked display (which worked before), but still no response.

What I’ve tested so far:

• I hear a faint buzzing sound when pressing the power button, but only if I press my ear to it.
• I feel slight warmth near the battery/logic board when charging.
• I’ve tried charging it overnight.
• No detection by PC (Windows or Mac).
• No visible burn marks, damage, or burnt smells on the connectors.

Theories I'm considering:

• Backlight circuit blown?
• Deep discharge battery?
• Possible PMIC or power circuit short?

Main question:

• Is there any way to confirm if it's actually logic board damage?
• Could it still be the battery or another component?
• Any tests I’m missing that could revive it?

I have basic soldering skills and want to learn microsoldering if necessary. Any advice is welcome!

Thanks in advance!