Chosen Solution
I was running out of space on my Mac Mini (late 2014) so I ordered the Mac mini Unibody SSD Upgrade Kit I used the external SATA USB adapter to erase the drive and format it to Mac OS journaled, extended. I didn’t install an OS or anything because my plan is to use it as a second, non-bootable drive. When I opened up my Mac Mini, I found there was no SATA drive, only the blade-style PCIe (250GB). So alas, I went back to ifixit and ordered the Mac mini A1347 (Mid 2011-Late 2014) Upper SATA Cable I installed the new SATA 1TB SSD and booted up (so now internally I have the old 250GB PCIe as boot drive with Mac OS Catalina, + the new SATA 1TB Crucial SSD). Disk Utility does not recognize the drive at all. I also tried booting into recovery mode and using terminal to run ‘diskutil list’ and it does not show up. I also tried resetting NVRAM and still nothing. Is it possible my Mac won’t recognize the SATA drive for some reason, since I have a PCIe drive as my primary bootable drive?
No, your SATA SSD should be visible. Let’s try this take the drive out with the cable and unfold any creases as well as put the system back together you should have room enough to plug the cable in before mounting the fan unit. I use a few books to hold the case with the drive dangling under it. See if the drive starts up that way. If you have an old HDD you could give that a try as well, placing your finger on the drive you should feel a bit movement when the system starts as the motor starts up. If not you may have a bad cable.
