If you are tech savvy, you can remove the 4 rubber feet on the back of the LCD (tablet side), unscrew the 4 screws and pop the cover off. The battery inside has a small connector on it which may have just come unplugged during shipping. Of course, you would have to be careful with the unit if you still need to return it. It does not have any warranty sticker to worry about, mostly just being careful not to scratch stuff.
I have another post with some pictures of the inside to help a little.