The drive likely has a hardware malfunction. You can try a new USB cable, but it's unlikely to help. These drives use hardware encryption and if they are unable to read the internal encryption key which is located in a hidden sector near the end of the drive they lock you out because the drive is unable to decrypt the data.
Even if you take the drive out of the case it won't help as the USB port is built right on the drive and there is no SATA port available to direct connect to the computer. It is possible to set up a SATA board to read the data, but as it is encrypted anyway that won't do much good.
You should look into professional data recovery if you need the data back. There is very little you can do yourself on these drives...