I checked it already in a button widget and it works for me without casting, so I still think that its a cast problem.
Try this:
1.Not the correct game mode is selected as your project game mode.
2.The game state not set correctly in the project game mode.
3.Removing the cast.
If all of this not working you can just tell me how you creating this widget step by step, or dropping of the packaged project and I come back to you in a jiffy.