Placing models on different height surfaces of background image

I’m trying to place objects on the podiums in my background image (attached). When I set the camera for the lower podiums, it's great, but when I place the objects on the tallest podium and move it up the Y axis, there's no shadow.

I’ve tried using cylinders as placeholders which works to get the object shadow, but setting opacity to 0 of the cylinder removes the object shadow.

What am I missing? I can't seem to find what to search for tutorials on this either.

Any tips are appreciated!