It's been over 10 years since I had an A1200 with a CD drive, but when I had mine I used the Elbox 4xEIDE interface and software as well, and it worked fine. I did have to install a file system that supported it, and I know I had a bit of trouble... some combinations of devices (different manufacturers) just would not work correctly as Master/Slave. I went through a few different devices, and occasionally had to configure them backward to what I thought was "logical" (i.e., set the CD drive as master and the hard disk as slave, or reverse their positions on the cable, try things like that).
Do you have any other drive you can try? Maybe a plain CD-ROM would have better luck than a DVD drive?
Also, try firing up HDToolbox or SysInfo, see if they're able to detect anything.
Good luck!