I have heard that withholding a meal, to sort of get them good and hungry, and put something really appetizing in there, something really hard to resist. Maybe give a few bites of it outside of the cage, and then put some in? Fancy feast appetizers, the grody fish ones are a HUGE hit with my feral, and with my inside cats....yes, I occasionally give my cats something gross, rarely, but boy do they love it! Also, temptations dry treats seem to be like crack to cats. Just some ideas!