Have the owner shut it down for an hour until the board memory is cleared of all messages. Have them unplug the printer for fifteen minutes more after turning it off. Then have them plug it back in and start it up. See if that helps clear the message board. Also, if they get the message again have them press and hold the green check button for 4 seconds, but only after you’ve gone through the first steps.
Thanks for that advise. She had shut down the printer several times, but didn’t unplug it. She unplugged it and then plugged it back in and restarted it. It appears to be working again. She asked me to say “Thank you”.