The problem is this. SCSI comes in many versions. Some require the person who configures the drives to set the SCSI ID and the termination. Your post didn't tell about that and the machine supplier should be contacted to find out how to setup the replacement drive. Much cheaper than a new motherboard.

Let me be blunt. SCSI is easy for those that configure it, but a mystery to most others. And given that all about SCSI is in textbooks at the bookstore and on the web, my choice is to give you guidance that configuration could be the issue is all I can do. You need some education about SCSI before you can ask the right questions and I can't do the education in this small space. Take time to research your SCSI configuration and call the place that supplied that setup.

In closing, read your post. No mention of exact make/model of the hard disk which would have opened the door to me being able to ask a question about jumper configurations and such. Don't fret about it, not many follow the forum tip.