To recover external hard drive that is not detected (https://notchox.com/resources/how-to-recover-data-from-external-hard-drive-not-showing-up/), first, use a different USB cable and port for it. If it needs a separate power source, you need to ensure its proper operation. It is necessary to check the hard drive on another PC in order to determine whether the problem is related to the system. It is also recommended to look into Disk Management on Windows or Disk Utility on macOS to find out if the drive is detected by the system. If the drive is detected there, one shouldn't format or initialize it. If there are any clicking sounds from the drive, you should unplug it and resort to hardware recovery.