Water damage- sound and vibration worked. Replaced screen- no life?

3-4 years ago, our tablet had some water damage near charging port. We held onto it because there was still sound/vibration after the damage until the battery ran out. This was before I had experience/knowledge on repairing electronics.

I opened it up and noticed no visible water damage on the charging sub-board, but water indicator sticker on it has signs of wetness. The sticker on the case near the top is ok, as well as the sticker near the sim card tray. I plugged it in with a voltage/amperage meter and the tablet is pulling in power. I tested the battery with a multimeter; it was showing ~3.5V.

I ordered a replacement screen and after connecting said screen, tablet would not turn on. I transferred the small parts from the old screen to the new. No change on the amp meter after the screen installation. I let it charge for ~30 min and tried to power on- no go. I tried to boot into fastboot, power+volume down- no go. Nothing has worked.

There is 0 sign of actual liquid damage. The LCD connector on the board looks good/undamaged, as well as the flex cable connector on the LCD. Any ideas??