The reliability of hard drives and SSDs is far from ideal - sooner or later, they fail, leading to serious problems, up to complete loss of the data stored on them. Of course, in most cases, the information (fully or partially) on the externally "dead" hard drives can be recovered, but you will need to turn to professionals salvagedata.com, as required special equipment and appropriate technical training. You can try to solve this problem yourself, but not the fact that you will succeed.