New SSD boots outside but not inside machine

Hello all!

I have been spending the last couple hours trying to troubleshoot this. Recently I have been doing Some 2.5 SSD swaps on my old MBpro unibodies all of which have gone relatively smoothly. I offered to do the same thing to a friends unibody MBpro who said his hard drive was messed up. I am currently having problems I have not encountered before , Here is what I have tried so far;

1. “Just give it a whirl” tried just popping in new SSD tried to recovery boot; no drive found.
2. Booted into a different instal of MacOS plugged in SSD and formatted it using disk utility. tried again to boot using internet recovery to make OS on SSD, SSD could not be found.
3. Booted Into Existing working OS HDD, used carbon copy cloner to copy everything to the SSD, rebooted in to EXTernal SSD everything works great SSD Clone works, I then went to put the SSD inside of the computer and attempted to boot nothing to be found just sad grey screen with a crossed out folder or the internet recovery start up.
4. I am starting to suspect either some sneaky apple whitelist firmware that has this SSD not working or perhaps a SATA ribbon cable going wonky.

I am currently writing this post on said Macbookpro running Mac OS on the SSD externally connected by USB which seems to work fine for some reason……? the only thing that is giving me some doubt about the Bad SATA ribbon theory is that the HDD that I was using worked internally for the most part aside from one unexplained crash during my first attempt using CCC…. maybe it is ribbon going bad? Anyone have a theory?