If the connected device is not powered by the USB connection, make sure it's properly connected to an electrical outlet. Make sure it's turned ON.
Try connectin using another USB cable.
Try connecting in another USB port.
Try another device in the USBport.
If your device works in another port and some other devices DON'T work in a particuliar port, it's a sign that that port, and often a second one, is defective.
In some cases, it may only be a mather of repairing a weld, or the controller for the port may be deffective.
If the controller is defective, you can't repair or replace it as it's part of the motherboard.
If your device don't work when connected to ANY USB port, even from other computers, that device is defective. Depending on the exact problem, it could be repairable, or need to be replaced.
Electro, January 2013