did you check all cables are connect correctly? did you go back and check again? did you double check your double check? if you're positive it's all plugged in correctly, try unplugging the SSD and connect the HDD to SATA_0 on the motherboard and then check for it in BIOS again. if that doesnt work, take out the HDD and punt that THANG down the street.
just kidding. report back after you do this stuff. we can go from there.