Well if the computer only has a USB 2.0 port and the device you are trying to connect is a USB 3.0 device, then it won't connect properly. While you can use a 3.0 port to connect a 2.0 device, the reverse doesn't work. You would either need to use a 3.0 port (if your device has one) or get yourself an external drive that uses 2.0.