Onkyo DVD player - remote doesn't function at all

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

You can get a substitute remote (the original remote is no longer available) at
http://www.remotes.com/remotes/servlet/rs?a=gmi&uuid=13118717212490&smodel=DVCP702&brand_pn=ONKYO_DVCP702
Let me know if you have any other problems or questions.Please rate this solution. Thanks.

If you turn the remote over there is a tab at the top push that towards the bottom of the remote and pull up. Once you have the battery cover off replace batteries with two AAA batteries. Click below for a copy of the manual. The battery replacement is on page 9 of 40 in the adobe document.

Onkyo DV-SP301 Manual

try these codes.
30503, 30612, 30627, 31612, 31627
If not, re-post.

Your Onkyo TX-SR304 receivers remote (RC-645S) is not capable of controlling devices by other manufacturers. It controls only Onkyo devices.
Other Onkyo remotes do have universal remote functionality and you can download Onkyo remote codes here.

I hope that helps.
________________________________________
Download Onkyo TX-SR304 users manual here.

You will either have to use your Onkyo remote to teach the Harmony those functions or try one of the similar model receivers in the Harmony software. I had to chose a similar DVD player in the list in order to get my Harmony to play nice with my DVD player.

Not sure I can solve, but maybe help. I am having a similiar problem. However, make sure you Analog Audio (RCA type) cable are connected even if using Digital connection between the two. They use those cable to send the Commands (Mentioned in the documentation).
If you did get yours to work, please give me a hint... I upgraded mine from a 603 to a 701 and haven't been able to get it to work since.

http://www.dvdexploder.com/multihacks.htm

http://www.videohelp.com/dvdhacks