What model ipad do you have? This has been reported. Those who have resolved it did a forced restart - on Face ID ipad it’s : press the volume up button, release then the down button, release and then press and hold the power button down for a while until the Apple logo appears. The process is different for older iPads. Those that did so reported that it worked and also connecting it to power and leaving it for a while may bring it back even without doing the restart.
I just had the same problem - all of the buttons and the touchscreen were not responding, but the screen would turn on when the device was plugged in. Magic keyboard and Apple Pencil did not work either. I tried a hard reset etc., but since none of the buttons were responding I couldn't even turn off the iPad. For anyone else with this issue, I was able to get it working again by literally just leaving it plugged in for about 20 minutes. That seems to be the only fix as of now unless there is a way to plug it into your Mac, assuming the iPad is already a trusted device. (2021 iPad Pro 12.9in)
That’s what I’ve seen reported several times. Plug it in, put it away and come back later. But it might recur until a new update is released, although I haven’t seen any reports of this happening.
That’s a mess. Hopefully there will be a quick release to fix this. I have quit the betas since 15.4(.1) since I haven’t had any issues and didn’t see anything that was added that’s of any consequence. Now I’m very glad I chose to stop. I’ll look at betas again when 16.3 is released.
