just say it just stopped working one day.
or it became defective.
but they might give you some things to try and tell you to send them some screenshots to see if your computer recognize it when you plug it in. Thats what they did with me, and since nothing worked, they told me to send it for replacement, but i didnt have no receipt or anything since i got it in china, so i opened it, got another external enclosure and it works fine now.