iPad error code 4013

Thanks for the quick response.

That support page tells you to turn the iPad off, wait 30 seconds, then turn it back on. I can't even get the iPad to show the Off slider regardless of the different combinations of buttons that I press.

Have scheduled a Genius Bar appointment.

Have pressed simultaneously both top/power and bottom/home button. Get Apple logo, then screen turns black, followed by single full screen red flash.

Have held down both buttons for several seconds. Logo flashes twice with about 10 seconds between flashes. Screen goes black even while holding buttons. Retry both buttons one time after waiting 30 seconds. Logo appears, followed by support.apple.com/ipad/restore at top, laptop/computer icon in the middle with connector cable at bottom of screen.

Plug iPad into connector attached to iMac/iTunes. iTunes shows iPad, says "There is a problem with the iPad “iPad” that requires it to be updated or restored." Have done this multiple times through iTunes, both restoring & updating processes. While attached to iMac, logo appears on iPad, followed by flash red screen, then support.apple ... et al as described in this first paragraph appears on iPad. iTunes has message box "This iPad could not be updated. An unknown error occurred (4013)."

Have pushed all the combinations of buttons which that page tells me to do. Only button that I haven't pushed is my belly button. iPad still won't show slider OFF.