A hard drive is not detected problem can result from bad connections, lack of power, old drivers, broken enclosure, problems with partitions, and hardware failure. When dealing with an external drive, try other USB ports and cables and connect your drive directly rather than using a USB hub. Windows users can also use Disk Management to see if the actual disk is detected. If the disk is detected, but you are unable to access the files, refrain from performing tasks like formatting which can interfere with your data. If the hard drive is broken and produces strange sounds, try to avoid using it. Notchox can be used in situations where you want to recover inaccessible files.
Read more - https://notchox.com/resources/how-to-fix-hard-drive-not-detected/