Hello and thank you for using JustAnswer.
He probably engaged the lockout feature.
To unlock the buttons on the remote control
by using the
touch sensor panel of the main unit (see page 24):
1 Press MENU to display the MENU screen, and then
press VOL up or down to select "System Options".
2 Press CH up or down to select "Operation Lock Out", and
then press INPUT.
3 Press CH up or down to select "Off", and then press INPUT.
4 Press MENU to exit.
• To unlock the buttons on the TV, press MENU on the
remote control, and then select "Off" in "Operation Lock
Let me know if this doesn't correct it.