You may want to give us a little more info to go on. Not knowing what year you have makes it a little harder to help you.
Some vehicles have an inline fuse in the wiring just before the 12v outlet. This is easily overlooked. Also check the integrity of the connections. Do you have a voltmeter? If so, there are several simple tests you can perform to isolate the source of the problem. Also, did you check both fuse boxes? You probably have one under the hood and one in the cabin on the drivers' side.
Again the more info you share, the easier it is for us to help you.