I would say it is the Battery, it sounds like the auto switch has failed. Since the auto switches have a small silicone rubber disc attached to a small metal contact steel plate they are very temperamental. That is why I prefer manual switches.
If it is under 30 days old, then I would contact the place you got it from and they might replace it no charge, if it is older than that then I have successfully gotten two
batteries working out of 4 by doing the following.
Pour a small amount of isopropyl alcohol in the cap, and dip the battery connector end in to the cap until the barrel of the battery is 1/4in into the liquid. Remove and "lightly" tap onto a paper towel, do this until the liquid that comes out is clear on the paper towel. Shake it it like one of the old mercury thermometers until no more liquid comes out. Allow to dry for at least 60 min. Then give it a try and see if it works. Like I said I have rescued 2 out or 4
batteries this way, and a lot of brown stuff came out from over filling the cart that ran down into the auto switch.
Hope this helps you
Dan