There are several different possibilities for this error. Here are the things to check (in order of most likely to least likely):
- Ensure that the board is powered. (obvious)
- Make sure the cable is connected and that pin 1 (VCC) has power.
- Check to see if the part is bad. Usually this is not likely, but an easy test is to use another board. If both boards have this problem, then it's probably not a bad chip. To prevent damaged parts, proper ESD procedures should be followed.
- 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)
- Try it with a desktop if you're using a laptop. Some laptops share 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. In this case, the manufacturers recommend using an external USB hub.
The ispDownload Cable is known as programming cable.