I had an alarming issue where one of my USB ports (the one closest to the display) wasn’t recognising any devices… It would charge them up without any problems, but things like USB hard drives and iPhones would not mount. I thought that this was a hardware fault, and was preparing myself book a slot at the Genius Bar.
However, by resetting my PRAM and NVRAM, I managed to fix the problem. To do this, first power off your Macbook Pro. Then, hold down the option key (alt key), Command Key, P and R simultaneously. While holding these keys down, press the power button once and wait for the computer to chime. Once your laptop has “chimed”, it will restart – you can then release the keys. Your NVRAM and PRAM will now be reset – and hopefully, your USB Socket will resume normal operation!
I hope that this helps!