2013 MBP unable to see new internal SSD So I have a 2013 MBP that I'm trying to install to give to my friend. I've bee running a 500GB Samsung Evo 850 for a few years. I'm trying to put in a 250GB one in. 

I've managed to install macOS High Sierra when in a usb cage I've got. It boots just fine off of my original SSD. So I don't think it's the cable or the ssd. 

I've been installing off of a USB installer I made using my new macbook. I've reset the SMC and PRAM. 

EDIT:

No idea what's going on. I've given up and left the 500GB drive in the computer while I keep the 250GB with my stuff on it on the side.
Is the new SSD properly formatted?
I’ve had issues before where the drive was still FAT or whatever, but the Mac partition was properly formatted and looked ok.