You can try any or all of these steps to help with this problem:

1) Remove the USB cable and re-insert.

2) Restart the software.

3) Missing Drivers. If this is the case please reinstall the software.

4) Factory reset the device by holding the button down for approximately 20 seconds until the LCD display indicates 'FAr5', then release the button.Do not be tempted to release when it gets to approximately 10 secs when the display will change to read 'r5t', make sure you keep the button fully depressed.  We do get a lot of customers who release too early and only reset the device!