After a couple of days trying to get my old iPad (6th gen) booting again, I gave up and purchased a new iPad (7th gen).
I had left it plugged into a charger over night. At some point it "turned on," but did not actually boot. I was able to "force reboot" it, but it wouldn't boot, always just a brief visit to the Apple symbol and switch to black screen.
I was able to get it to reboot in "restore mode," and the MacBook Pro tried to restore it, but failed with a not-helpful (and not on the Internet) code. I got it to boot one more time in "restore mode," and started another restore. I very carefully left it alone, with the MBP screen left on (hot spot). I left to tend other things, and returned to a blank-screen on the iPad and a different unhelpful message.
Since then, I can "force reboot" it, and it keeps going through the Apple screen to the black screen, but nothing I can do can get the MBP to recognize it as a device, needing restore or not.
None of the Apple stores are open near me for a better hand at fixing it. The closest is almost 300 miles away. The Apple site points out the iPad is out of warranty, and has no Apple Care, nor one offered for a late purchase. Alas, their estimated repair is like $400, which is more than a new one.
I vacillated over going with the iPad Air, which has the A12 CPU, but then most of the stores nearby happened to have a $100 off sale on the iPad 10.2-inch, 7th gen. So I slipped one in the e-cart, and headed off to pick it up.
Of course, the new one worked out of the box. It's a little bigger than the old 9.7-inch. Feels a touch heavier, or maybe it's just skewed because it's a little longer. If I didn't have the old one in hand, I probably would be hard pressed to tell the difference. Except the old one is the "gold," which has a white frame around the screen, and the new one is "space grey," with a black frame.
I let it restore my last iCloud back-up, from the day before it stopped working. It took a couple hours to let it reinstall all of the apps, but then it just worked. I had to add a few passwords, and the terminal app I use didn't keep any of the settings, so I'll have to reconfigure that. There are also some apps added through the office that didn't come back, but they'll be easy to add.
Otherwise, it works fine. It's nice to have the internet in the palm of my had again, bigger than my phone, anyway.