Just ran into this bug this morning. My wizard casts the Light cantrip on himself and the little purple dot appears on his character image indicating that he has the light cantrip active, but there's no actual light emanating from him. Mechanically I'm guessing that once the cantrip is active he no longer suffers the penalties for being in dim light or darkness, but I'd actually like to have the light to navigate by!
Anybody else experiencing this problem? Or is it just me?