There are several different possibilities for this error. Here are the things to check (in order of most likely to least likely):
1 - Check to see if the board is powered (obvious).
2 \u2013 Check to see the cable signals are correctly connected to the board header.
3 - Check to see if the part is blown.Usually this is not feasible, but an easy substitute is to use another board.If both boards have this problem, then it's probably not a bad chip.To prevent future blown parts, proper Electrostatic Discharge (ESD) procedures should be followed.
4 - Try another cable. Sometimes it's a cable issue. If not properly handled, cables can also be damaged (since they do have internal circuitry and are not just pure cables)
5 - Try on a desktop if you're on a laptop. Some laptops share power between their USB ports, so an individual USB port may not be able to provide enough power. This should only be an issue if you have other power-consuming items plugged into the other port(s). However, it's been seen even when the cable is the only thing plugged in.The manufacturers recommend using an external USB hub in this case.