I have recently upgraded to SSD (Samsung Evo 850) from HDD on my MacBook Pro Mid-2012.
However, the installation of SSD has been very painful. I tried to use Disk Utility in recover mode many times but it would fail either to erase or mount the SSD, even though it recognized that the SSD was plugged in. I thought it was the faulty SSD.
Then I hooked up the SSD using USB and proceeded to install OS X on it (using my HDD). The SSD functioned very well using the USB, so I put it in, and hooked up using the flex cable that was previously used for my HDD. However, it doesn't function, the OS sees that there is a drive hooked up, sees the name, size and etc, but won't load, gives me the question mark folder sign, when I try to verify or repair the disk, it fails to do so.
So I think it is something with the SATA cable. But the cable functions perfectly when used with the HDD. So I was wondering if the HDD cable that comes with MacBook Pro Mid-2012 is compatible with SSD. I have watched several videos of people upgrade from HDD to SSD, but they all seem to be using the same cable. Any ideas what might be the issue or if I need a different kind of cable?
EDIT: The issue has been solved. As people have suggested here, it was just a faulty cable, or just the original cables don't work with SSD. I bought the same cable, 821-1480-A from a vendor on Amazon and it works quite well with SSD for now. Thanks everyone for your help.