The server's manual recommends filling the drive bays in the 1,2,3,4 order. At this point, you should check the HP support page for the server, Look for controller firmware updates, BIOS updates, troubleshooting advice and so on. Did you try to connect the drive alone? If it is detected alone, you will have a clue there. Some drives don't go along with some others when installed in the same pair of ports, for example. I would also suspect the cable. I have had more problems with SATA cables than I could expect. Also, the drive itself can be defective. I once received two new WD high end drives that couldn't be detected by any controller and I had to return them. The new ones worked fine.