Built a new pc only recognized the ssd in the bios, stumped

I recently built a new pc. I’ve built them before, so I know what I’m doing. I wanted to transfer my old hard drives to my new computer so I unplugged them and plugged them in the new rig. Upon booting up I noticed it only recognized the ssd in the bios. I un plugged and replugged and restarted in all the sata slots and made sure the hard drives were indeed powered and spinning. Then it stopped detecting the ssd entirely and I couldn’t get past the bios. Defeated I took my hard drives out of the new rig concluding that I had a faulty motherboard, what a nightmare. Upon replugging the hard drives into my old rig however the nightmare got worse as this trusty old rig that I know to have worked with these particular hard drives and in fact had just used them the day prior now only detected the ssd as well. Idk wtf happened to my hard drives. Did I destroy them or something or is there an easy fix? They are pre partitioned and don’t show up in the bios, os, this pc, or disc management. They also still spin when powered so idk what is wrong. Someone experienced pls help, I need these PCs and hard drives up and running asap. Thx.