I have installed two of your units and everything went fine until it showed the notation: "The device is currently unavailable." Admittedly, I'm not the best informed computer user and can't make sense of most abbreviations used in a Word.
This could mean:
The hard drive has crashed and it can't be recovered. You need the help of an IT technician.
The drive is not properly connected to the cables. Open the device, then connect the cables.
The drive has BAD sectors which means you have to backup the data as soon as possible. Connection to another PC is recommended in this case.
Note: If you have data on the HDD, do not attempt to fix it by yourself.