Hello, everyone. I have this problem where my external HDD doesn't get detected. On an old laptop with Windows 7, it gets detected, but it won't open. On Fedora, it doesn't even get detected on the whole system. In the KDE partition manager it does show up as "sdd", but it will not show up in Dolphin or in the terminal, when manually searching for it. It's a WD Element external HDD. I think it's formatted with NTFS. I have lots of important data on that drive, so reformatting is not an option. Not only that, but I haven't dropped the drive, nor have I done physical damage to it. It's only about a year old.
It sounds like your partition table is corrupted. Recreating it (with parted or fdisk) shouldn't affect the data.
Also, I believe that if it shows up as a block device, you should be able to copy it with dd. dd can write to another block device or to a file (like an iso).
After further investigation, I decided to mark the hard drive as corrupt. Fedora 38, Debian 12, and Windows 7 will not detect the drive, so I will send it to a data recovery institution to get my data. I honestly do not know what happened.
Not sure if you already sent the drive away but I would recommend checking the output of 'dmesg' (as root on most distributions) after you plug in the drive. It might give a clue as to whats wrong.
It could just be the enclosure or power supply of the enclosure. Can you hear/feel the harddisk starting up? You could try opening the enclosure and just directly install it into a PC if you feel comfortable working with hardware.