Rebecca,
I would make sure that the terminals on the battery are clean, you can use a pencil eraser to do this. I would then check to make sure the power supply / power cord that you have is functional. Is it powered via USB cable? USB mini and USB micro cables wear out and stop charging devices like they should, you can also check the power adapter that the USB cable plugs into to ensure it is putting out 5 volts as it should. The easiest way to check these things is to find a spare cable around the house and a spare AC to USB adapter around the house and swap one out at a time to find the culprit. I hope this helps.