I've got a couple INV objects with floating glass panels behind them and a couple of lights - all generated within an INV scene. I'm having difficulty having my objects cast shadows onto the glass panels. I've got cast shadows on for key and fill lights and I'm not using AE lights.
Did you update your lights in the Scene Preview window?
Check also if your objects may not be too far from the transparent panels.
Another thing to consider is that if your panels are highly transparent the shadows will be too.
Therefore, to make your shadows appear less opaque you would need to add a reflection map to your panels. Avoid having a high shadow softness value and/or a low shadow darkness value.