Why did my hard drive cable repair not work?

I have a Macbook Pro Mid 2012 and a question mark with the folder started popping up on the 15th of January. I did some research and I was able to hold down command R and try to repair anything wrong with the Hard Drive and it said everything was fine. I was able to unlock my hard drive ONCE and continue working on my laptop. I closed it for about an hour and came back to continue working on it and the same thing happened except it would not work anymore. I tried unlocking the hard drive and restarting it. Tried reinstalling Mac OS X Mountain Lion and said my hard drive already had the latest version. I tried repairing everything on the hard drive and everything was still fine. Eventually my hard drive stopped popping up, so I took it to the help desk at my college they searched the serial number to assure it was a 2012 and what part I needed, so I ordered a new hard drive cable from amazon because it is a common problem with this model. I took it to the school help desk and they watched me go through each step as it is an easy replacement and made sure I did everything correctly but it didn’t work. The hard drive did not read so I took it out and tested a hard drive and hard drive cable in my laptop that the school had. It booted just fine, so I then tested my hard drive with the hard drive cable from the school and held down command R, my hard drive read, I unlocked it, restarted it, and it booted up. I unlocked my window and everything was there just how I had left it. So the Hard Drive is fine it works. I tried to put the hard drive cable that I ordered from amazon back in one more time and it boot up and didn’t read, so that left me to the conclusion that the Hard Drive cable was bad and I figured that would be a possibility since I ordered it from Amazon and it was cheap. So I went ahead and ordered a brand new hard drive cable with a brand new bracket attached and already put together from iFixIt. I took out the amazon hard drive cable and replaced it with the iFixIt hard drive cable and still no luck. The computer is still showing the question mark with the folder and My hard drive is not reading when I hold down command R.