I am getting the same thing. Removed the profile, and re-added. Restarted the phone. Cleared some space even though I have plenty. This is the error... software update failed an error occured downloading ios 16 developer beta

I am still having the same issue in 15.6 beta. Some users are saying this has been fixed, but I am still unable to use the pencil. Not even when out of the keyboard.

Sorry...just noticed there is already a topic for this.

Same here...it seems to be the keyboard. When I take the iPad off the Magic Keyboard the pencil works again. Add the keyboard, without attaching the pencil to the iPad magnet the pencil still works. Once you attach the pencil again while the iPad is attached to the keyboard, the pencil stops functioning.