3D Widget invisible during preview

I have a simple 3D widget of a digital display on a model; in the editor it looks exactly as I’d like; yet when I press play, the widget appears to be hidden. On a whim I tried setting it to 2 sided and flipped it over. When I do this I get a black silhouette in the shape of the widget. There is no code at all in the widget so there is nothing to interfere with the visibility. Anyone got any ideas?