There could be a few reasons why it's not opening - first, the DVD drive itself could be faulty. Maybe it's a power- or motor-related issue, and it won't work until it's fixed. Another option is that ...

I had a similar experience with a PS2...I dropped it in transport (~2 foot fall, but on a hard floor). The disc tray popped out, and the eject mechanism was completely fouled...wouldn't push it in or ...