2011 MacBook Pro won't see SSD

I was given this nice 17" 2011 MacBook Pro. It had 10.9 installed and only 4 GB of RAM and a super slow hard drive.

A friend sent me an old 240 GB SSD he wasn't using, so I installed it but alas, the Mac won't see it! Any ideas why?

The drive needs to be formatted or the volume structure got damaged or corrupt?

Nope. When I say the Mac won't see the drive, I'm not just talking about mounting on the desktop. If you open Disk Utility, you can't even see the hardware. Its like theres no drive installed in the machine. I know this from NetBooting the machine off another volume.

The SSD is probably just dead/broken/damaged!

Before trying to use this SSD in this machine, I put it in a USB drive dock, migrated an installation of Big Sur to it, and booted another machine off of it. The drive definitely works. I reformatted the drive before I copied an older MacOS to it for this older Machine.

Then is has to be the Mac! It's SATA controller or cable or something are bad!

But alas, I can and have put the original HDD back in this machine, and it boots right up! It's running right now off it's original HDD. It makes no sense that the computer could see an HDD but not an SSD.

Those are the three obvious troubleshooting areas and they all test out fine. And yet, the Mac repeatedly still won't see the SSD. Including when booting the Mac while holding the option key. Or when booting a 10.9 installer, or a 10.11 installer. I'm out of ideas!