I know this might sound dumb but to be honest this works for so many people. Lithium cell phone batteries and most lithium batteries have what I like to call a safety switch built in so it will not allow its cells to go so low that cant come back to life at all. Think of it similar to a car battery. When the car battery cant give enough energy to start the vehicle also known as crank voltage it has the help of the alternator to rejuice it up a bit. You can literally jump start or quick charge your battery. Takes 10 min and once the battery gets to a certain level it will continue to charge normally. It just got so low n activated the safety mechanism which is to play dead like a possum. Good luck. There are videos on this. I suggest having or getting a cheap multimeter so you can check the power. Your welcome.