GND Pins are not connected to GND plane
The problem you are facing is due to a mistake in the library.

On examining your library it becomes apparent that you have placed a drill hole directly on top of your through-hole pad:



If you delete the drill hole (through-hole pads have a drill hole already so don't need another), all works as expected:



You have the same problem on the hole for the + pin as well - an extra drill hole. If you run the DRC in eagle it will tell you the issue (Error - close or overlapping holes or something similar).