i haven't read through all the responses but I have an ex feral cat that also refuses to use the liter box. I finally found a solution, he likes puppy pads. I line a liter box with a puppy pad and he uses that to pee. pooping is still not done in the box but that's an easy clean up. For some reason, he just doesn't like any type of liter but will go on the puppy pad. good luck!