Hi ! I've got an issue with my 2015 retina macbook (the one port boys), that doesn't want to charge its battery anymore. It just started saying "battery is not charging" a few days ago, but it will take power from the charger because the battery levels are also not depleting (or extremely slowly). It also won't power on a usb drive or an external hard drive, but it will run on battery power when it is not plugged in. Any idea where the problem might be coming from ? Thanks in advance.