I can't find any reference to that error message in the service manual. However, this might be related:
The Panel Menus lets the system support person enable or disable the control panel menus. Selecting On (the default) allows users to chance values for the printer. Off disables the users’ access to menus. If a user presses Menu, then they receive a message that the panel menus are locked. When set to Off, this setting restricts all menu access, even to menus or items set for PIN access, However, when set to On, all PIN restrictions are restored.
This menu item appears only when the PJL PASSWORD Environment variable is set to 0
