Replaced Harddrive cable, yet still won't boot SSD

One day, my Macbook pro was unable to fully boot; my Samsung 850 SSD was unable to be read. After some testing I found that the SSD itself was fine; I was able to boot externally via USB and also internally in another friend's Macbook. I figured the SATA cable might have been the problem so I bought a replacement and installed it.

With the new harddrive cable in place, the SSD, at first, wasn't able to be recognized at all. I did another clean OS install, and it finally showed up under the hard drive options. I waited for the loading bar under the apple logo to finish, but realized it was extremely slow. When it begrudgingly reached the end, it was stuck there, and after a few more minutes, the screen would turn black, but the computer was not off. But when I switched the SSD to an HDD, and it booted up perfectly fine; fast loading time, no black screen.

Things I have done so far:

- Booted SSD externally via USB (worked fine)

- Clean reinstall of OS onto SSD

- Reset PRAM

- Made sure EFI and SMC firmware are up to date

- Reset SMC (SSD still gives black screen after this, HDD is fine)

- Tried to use another SSD, did not work.

Other people have had success when replacing their harddrive cables for their SSDs, but this doesn't seem to be the case for me. I sincerely made sure I installed the cable carefully as per instructions. I have also read about the tape trick, but it seemed to be only a temporary solution until a new cable is to be purchased. Since this is a brand new cable, I am at a loss.

Any help would be greatly appreciated!

Edit: I just realized the sensor bracket LED for the new cable does not seem to be working (doesn't pulse when the laptop is closed) ... I switched it back to the original cable and the LED is working fine. Could it be my cable is faulty?