Chosen Solution
So, about a month a go i bought a Samsung 850 EVO (1TB) . Suddenly my new SSD starts to boot very slow and at some point will freeze up my laptop. Upon research, i manage to find a way to boot it up with via usb with this https://www.startech.com/HDD/Adapters/US…. and works perfectly. But when i place it in internally it won’t boot up. Any Help? Thanks.
Probable bad hard drive cable. Replace with a new one from the 2012 13" model. Buy a new cable only! MacBook Pro 13" Unibody (Mid 2012) Hard Drive Cable
