I’m also assuming you’ve created this bubble in the default orientation (X-Z) so if you’re using a point lamp, try moving it along the Y axis (You can do this my hitting G-Key to grab, then Y to constrain movement to only the Y axis). If it is behind the GP Object, it won’t show anything. If it is in front, usually when it is really close, this should show the light effect. Once you have a position, tinker with the intensity and further position until you get a result you like.
