The DVD player seems to immediately attempt DVD mode upon powering on, despite no disc being present. The display shows "ERROR, PRESS POWER OFF/ON TO RESTART" and no other action is possible other than to power off

What is the model number of your DVD player? You may try power resetting the unit and check if it helps. To power reset, turn OFF the DVD player and unplug the power cord from the electrical outlet for 30 seconds. Plug the power cord back into the electrical outlet and turn the player ON. Attempt to open the disc tray.

Depending on the model number of your DVD player, simultaneously press the POWER + STOP + EJECT buttons. If the disc tray still does not open, simultaneously press the DISC1 + STOP + EJECT buttons.
NOTE: This step may not apply to all models as DISC1 is not available on all DVD players.

If this does not work and if the DVD player has DISPLAY and PREV buttons, press and hold the DISPLAY+PREV buttons for two seconds to unlock the drawer.
***********************************************
FOR SONY PLAYER's

This issue may occur if the disc is damaged or if the disc was not inserted properly into the Blu-ray Disc® player. Follow the steps below to open the disc tray and eject the disc.

1. Turn off the Blu-ray Disc player.
2. Disconnect the power cord (mains lead) or AC adapter.
3. Allow the disc player to remain without power for 30 seconds.
4. While pressing the OPEN/CLOSE button located on the front of the disc player, reconnect the power cord.
   IMPORTANT: For some Blu-ray Disc Home Theater models it is necessary to press and hold the OPEN/CLOSE andPLAY buttons simultaneously, then reconnect the power cord.
   NOTE: This step may require the assistance of a second person.
   
5. After reconnecting the power cord, when the tray opens, release the OPEN/CLOSE button.
6. Remove the disc.
7. If necessary, disconnect and then reconnect the power cord to recover the player.

You may try power resetting the unit and check if it helps. To power reset, turn OFF the DVD player and unplug the power cord from the electrical outlet for 30 seconds. Plug the power cord back into the electrical outlet and turn the player ON. Attempt to open the disc tray.

Depending on the model number of your DVD player, simultaneously press the POWER + STOP + EJECT buttons. If the disc tray still does not open, simultaneously press the DISC1 + STOP + EJECT buttons.
NOTE: This step may not apply to all models as DISC1 is not available on all DVD players.

If this does not work and if the DVD player has DISPLAY and PREV buttons, press and hold the DISPLAY+PREV buttons for two seconds to unlock the drawer.

Hello, I am sorry about you issue. It sounds like your player needs to be serviced. I have included a link to search for an authorized service center. Thank you, Onkyo USA
https://www.onkyousa.com/Support/servicecenterlocator.php

Physically unplug power from the unit for a minute or two.
Connect power cord to unit and Simultaneously Press & Hold
both the [STOP] and Channel UP [^] for 5 seconds. This will
force Eject the DVD tray. Remove any disc if present.
Cycle the power again if necessary and wait for the unit to
go through its self check cycle. If after several attempts, and
you continue to get this error, then your Ram drive may need
to be replaced.

Hello
The failure is of fan only, fan may be damaged. It can be replaced with and other fan. take it out, and go for an other same type. If the whole system is dead, it should be due to the fault of its power inverter board, and should be ckecked well. If power board has some trouble, front panel display also will not be there or display will be present, but no other functions, like load disc or unload disc, play etc won't work. From these make sure which part has the trouble and go on. You have pointe out the fault of the fan only here. OK.

Hi,
Please check door mechanism as explained in chat session and possibly loading belt and/or door switches could be culprit and causing problem.
Hope this will help.
Thanks.

Plug the power cord back into the electrical outlet and turn the player ON. Attempt to open the disc tray. Depending on the model number of your DVD player, simultaneously press the POWER + STOP + EJECT buttons. If the disc tray still does not open, simultaneously press the DISC1 + STOP + EJECT buttons.6 Jan 2013

Solved: DVD is LOCKED will not eject. please help. Manual ... - the ...

https://community.sony.com/t5/Home-Theater.../DVD-is...will-not-eject.../td.../55919.
or try this link. Dvd player will not eject or play dvd Google Search

I did try removing the Hard Disk from the recorder and did a diagnostic and fix-disk using Ontrack software. Ontrack showed no structural and physical defects on the hard disk. I replaced the hard disk in the recorded and guess what! Please wait, please wait, please wait, please wait...................................

XD-DV480 Multi-Region: Converting the player to an alternative region:

• Supply power to the unit and power on from standby mode via the remote
• Wait until No Disc is indicated on the fascia
• Now press Pause followed by 3, 4, 2, 2, 9 and then 2
• The display should now read CODE
• Now press 0, 0 for region free or 0 then 1 for region one, 2 for region two, and so on (Note: RCE discs will require specific region set)

If the above modification fails to work then the alternative method below may work:-

• Connect the DVD player
• Use the Remote Control to turn power on
• Wait until No Disc appears
• Press Pause and type the following code, 8, 9, 2, 6, the display will show "CODE__"
• Within 5 seconds press 00 for all regions
• Press Pause and Power

This should work for you.

Unplug it for 10 seconds then plug it in again