I'm not sure what color you painter painted the molding but you can use a brighter white paint on the crown such as super white or white from Benjamin Moore.

Or try having them paint the bottom edge of crown the same as the wall color or shade darker on walls

I think shiny white is a mistake. The trim is supposed to represent plaster moulding and as such should be flat. I would prime it again and paint it in flat, but in the same colour as the walls. This will give your room a lovely effect, with nice detailing and higher-seeming walls.

I agree, it should be flat not gloss.

Perhaps painting the ceiling a white with hints of beige as opposed to a flat white. The crown molding will then pop against another colour as opposed to white against white.

White, contrasting (unless white walls) is my favorite. Flat paint would be the proper paint to mimic history, but I'd chose a washable flat or really low sheen...because there will always be cobwebs and random dust up there. It just happens, and once you smear that on white paint, look out!

Also, I'm not sure what the rest of the house/room looks like, but generally what makes crown "pop" is the ability to "reveal". Once the shade and shadow hits it, it should stand out regardless. Painting the ceiling a very light version of the wall color works, but I say just paint let the lighting do the job of letting it pop.

Thanks for all the great comments!

So, might part of the problem by that the can lights do not have their trim on and the light is flooding out too wide, causing the semi-gloss to reflect too much?

You could try painting a section of your ceiling two shades lighter than your wall color for contrast, to see if you like it before painting the entire ceiling.

Paint the ceiling the wall color as feeny suggested. You will love it!!!

ET, partly. A lower sheen will still give you better distinction, even with the light trim on.

I painted my trim super gloss white between the flat white ceiling and the white wall. I think it rocks! But the room is very bright to start with and there are a lot of colored accents.

Try a satin finish try using the ceiling color for the trim