Why isn't my mac charging/ SMC not resetting?

I have a 13 inch, mid 2012 macbook pro. It is plugged in but not charging (although it is keeping it at the same charge). The magsafe light is green even though it is not fully charged. I attempted to reset the SMC using the method in which you turn off the mac and press control, option, left shift and command at the same time but it did not reset (I tested this by changing the energy saver settings and then attempting to reset the SMC. I then checked the energy saver settings and they did not reset). I also tried using a different charger. Any Ideas how to fix this?