I had a problem where battery was not detected and it was not charging as well. The backlight stopped working..I tried reseting SMC and PRAM using the key combination but it did not work. I latter opened the case on MacBook pro 13 (2015) A1502 model and unplugged the battery and charger. I pressed the power button with battery&charger unplugged for couple of seconds couple of times. The tried the key SMC reset key combination as well ( This step does not make sense but I did). Plugged the battery and started the MacBook pro and everything started working. Battery is showing, charging and backlight working.