Hi there,
You might like to give a few options a try.
1. Try a different USB port, if using USB 3, try on a older USB 2.
2. Try different cable.
3. Try on a different machine and see if it can detect.
4. See if your drive can be detected in BIOS.
5. Lastly, when you connect the drive, see if its vibrating a little. If totally no movement, other than SSD, its probably dead.