There are several possible causes with USB issues...
Probably the most common is the issue caused by the USB cables themselves ( besides a possible bad cable that is )... There are two types, one is for power only ( ie a charging cable ) and the other is a data cable ( power and data ). With the number of devices that charge through a USB cable, many people get their power and data cables confused and when they connect using just a power only cable, they forget ( or don't know ) to try their other cables.
The next issue actually shouldn't happen but it does... Many newer systems have a mix of different USB ports... USB 1.1, USB 2 and USB 3.x. The USB 3.x ports aren't alway very backward compatible with the various devices we have. So if you have the option, make sure to try the USB 2 ports ( when available ).