New Seagate SSHD not recognized internally, but OK with external USB
I purchased a Seagate Thin Laptop SSHD (500 GB) to upgrade my factory hard drive. I have formatted it according to all of the instructions I have found (Mac OS Extended Journaled), GUID Partition Table, when it was installed externally. I cloned the original drive using Carbon Copy Cleaner, swapped them so that the new drive is now internal. It is not recognized at boot, so I boot to the original drive (now in USB enclosure) and the Disk Utility does not even list the SSHD. I reformatted and, this time, just installed Yosemite on the SSHD (instead of cloning) with no better luck. No errors when Verifying disk.
My original HDD is still recognized internally as well as a different SSD, so I don't think it's the SATA cable. I can successfully boot to the new SSHD when it's in the USB enclosure. Help?
Is this a good question?