Check your cable, (Inspect every inch for any damage) Try and swap with known good cable.
Try disableing in the SCSI Bios (CRTL-A) Features for the drive.
If Fdisk is finding it, but unable to format it, most likely it's dead. IF Fdisk is not finding it. Check the System CMOS F1, F2, DEL, or INS. And make sure that SCSI is enabled, (Some systems disable it on failure as a failsafe)
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