|There are two components included in your external drive. The first is the enclosure. The second is the hard drive itself.|
The enclosure should show up in Device manager. If it doesn't that may be an indication that the enclosure circuitry has failed. In that case you could try removing the hard drive from the case and connecting it directly to a computer internally. Be apprised that doing so will void any warranty on the unit, if one still exists.
You could also try removing and connecting to a USB port using an adapter. See the link below.