Your optical drive should have two cables connected to it, a data cable and a power cable. If its a SATA drive it has a SATA cable and a SATA power cable, if its a PATA drive it has an IDE cable and a 4 pin molex power cable. If you dont have two cables plugged into it it wont work.
If you have both plugged in you can narrow it down a bit farther, check and see if your optical drive is recognized in BIOS, if its not then go through and double check your cables to make sure something didnt come loose.