Do you hear the drive spin up? Do you hear the heads seeking or any other noises? If not, double check that you have power connected to the drive. If you can hear it making noises, then double check your data connection. Double check the jumpers are correct. If you still can't access it, the drive electronics may have failed.
If the data is critical and you are willing to put in the effort, you could try buying a known working model of that drive from Ebay or other source and swapping out the PC board from the good drive to the one you are trying to recover.
