Can't see your new SSD after installing OS X? You could have a bad flex cable.
If you have made sure your drive is partitioned GUID and you have not cloned it using Carbon Copy Cloner (Search CCC SSD issues) then you are probably looking at a bad flex cable.
- New SSD can boot from external USB but not internal.
- When booting to new SSD you get a circle with a line though it.
- New SSD cannot be selected from Startup Disk and says "This drive cannot be blessed"
- Old HDD boots up fine.
Why does the old HD boot and not the SSD?
Well I'm not really sure but 99% of the time if you have the symptoms above then it's the cable that needs replacing. So where do you get a new one and how do you replace it? Just go over to ifixit.com and find your model. They have plenty of repair guides and might even have the part your looking for.
How do you find the part number?
Once you find your guide and pull the old flex cable out the part number will be on the cable and read something like 821-1480-A which happens to be the 13" Macbook Pro mid 2012 HD flex cable. This also happens to be one that has failed on me many times.
Ok I have the part number, now what?
Amazon is your friend. Just put that part number into an amazon search and your all set. Just be sure to buy one that is a little more expensive than the cheap one.