You can't open the disc tray by pressing the “eject” button when the set is in standby mode.
The correct procedure is to press the “power on” button to turn the set on first and wait for 5 seconds before pressing the “eject” button.
The set needs about 5 seconds to finish the initialization process after power-on. If you press the “eject” button immediately after power-on, the tray cannot be opened.