Unlock the layer you have the crop marks in and double-click it. Layer properties will come up. Make sure that you have the check box ticked for "Print" if that isn’t checked off then the layer will only be visible on screen and won’t print. With this being said, I usually just combine all my artwork and the crop marks into one layer set the layer properties and then make a layer on top of that for the cut paths. Hope that helps.
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