Re: Crucial MX500 500GB not showing up in "Mid-2012" MacBook Air
I believe you have a MacBook Pro since the Airs only had proprietary SSDs available. If you have a MBP 13" (mid 2012) then the Hard Drive cable should be replaced as it was a very common failure for that model. Even if you don't have that model, replacing the cable is your best bet after resetting the SMC (you can use the keyboard option too) & PRAM (make sure you hear the startup chime at least three times before releasing the keys). It is best to do these two resets back to back.