I've never heard of this controller before this post, maybe it wasn't sold in the US. Looking on the net, the ad says it's good with WB 1.3 and above. I'm guessing it might be rather old and may not support HDs in the Gigabyt range.
Can you confirm this HD and 50to68 converter on another Amiga SCSI controller? I don't remember the other systems available to you.
Did the previous owner of the controller use it on his system? Can he help?