Mac doesn't start up

[JuIez]

Hi guys!

Today, my MacBook Pro 13" Mid 2012 (with Samsung evo 840 sad) started having serious problems out of nowhere to boot properly.
I just got a flashing question mark when i tried to start my Mac. Doing some searching I found the following article by Apple: https://support.apple.com/en-us/HT204323

Unfortunately none of this helped because I wasn't able to delete or even repair the volume. Even worse, the volume doesn't appear on disk utility any more. So I decided to put the ssd into an external hard drive slot and voila, the ssd showed up again, I deleted it and installed OS X Mountain Lion through the Internet recovery. Everything went fine there. After the installation was completed I inserted the SSD into the MacBook again. First boot up, still perfect. But after a second reboot I am back at the beginning. Question mark appears again and in the Internet recovery menu isn't any sign of the ssd. Can't choose any drive

At this point I am kind of perplexed and looking for some advice.
Thanks in advance!

 

[treekram]

It's probably the drive cable. They have a tendency to be or go bad, especially if your 2012 MBP is an older one (one can have a 2012 2012-model MBP or a 2016 2012-model MBP). Typically the cable will work with a HDD but not a SSD. You should do diagnostics to make sure there isn't anything else going on. If everything else shows up OK, you can get a replacement cable such as:
https://www.ifixit.com/Store/Mac/MacBook-Pro-13-Inch-Unibody-Mid-2012-Hard-Drive-Cable/IF163-041-1

You can look elsewhere for a better price but the iFixit site has the Apple part #'s that you can use to search other sites.

 

[SgtPepper23]

If you've got another Mac and a hard drive reader, I'd suggest you use that first, to test out the SSD, to make sure that it is still okay, before going ahead and buying a replacement cable.

 

[JuIez]

Thanks sooo much guys. Just received the new hard drive cable and everything is working fine again!
Really appreaciate your help!