I got it from a yard sale. it won't turn on. if plugged in it shows the dead battery symbol, Apple logo, turns off and repeats. iTunes won't detect it unless in DFU mode. recovery fails on waiting for iPad(unknown error).
This happened to me with newer iPads and even my iPhone XS Max. Let it charge using the Serial cable. Leave it on the charger for at least two hours. Then try to turn it on, connect it to iTunes, and go from there. That helped my boot loop.