Turned on Mac - couldn't see hard drive. Tried to reloaded IOS, no hard drive. Bought new hard drive, Mac still couldn't see hard drive. Found thread about this issue, so I swapped out Hard Drive cable with another Mac - YEA - hard drive now there.
Perfect. Purchased new cable from iFixit and it arrived 2 days later. Installed - booted - all perfect.
It really helps to have a spare mac to use for swapping parts and trouble shooting. But this is a known issue with this run of MacBook Pro models. The cable assembly fails. It's not the cable itself it's the IC that is part of the assembly.