Hi,
Looks like I have the same problem, I recently replaced the eject belt on my JE440 following the many youtube guides. However when I had it back together and plugged in the machine goes to standby and no further. I can't get it to turn on with the facia button, remote, or by trying to load an MD. I followed the on line instructions carefully and everything unplugged (two data cables) has been carefully reattached. The only thing I noticed in my machine did not have an earth wire connecting the optical drive to the chassis that was present in all clips I watched? Any advice on what I may have done wrong would be appreciated as I don't want to throw the unit away? In the mean time I will have a go at removing the top of the drive and see if it resets.