This MacBook Pro was upgraded with an SSD, few months after came back with the "Question Mark" Folder, done checks, replaced SATA cable. All good.
Now back again with the "same problem". Done checks.
- SSD will not show (in Disk Utility) either from SATA or USB
- SSD will show and boot on or other machines.
- MacBook pro reads other Drives, USB, and even SSDs.
So conclusion, it's just this SSD that it doesn't want to read.
Now in the ideal world, I would understand why this is happening before swapping a 500Gb SSD without knowing the reason.