External hard disc drive repairing software

So you have portable drive (powered by USB 2.0). Does your computer has USB 2.0? Have you tried different USB cable?

If the drive does not show up in Disc Management, or when you plug it in another computer, or not recognized when booting with Linux, then

either the drive is defective or
enclosure is defective.

With bad enclosure, you could crack it open, extract the hard drive and plug into another enclosure. Do it at your own risk.

The drive may be damaged.

If it asks you to format, you need to format. If it does not and it's still unrecognized I suspect the drive is bad.

You should contact the manufacturer, but I suspect you'll need to return it if it's under warranty (RMA).