Yes I tried that.. I used detol and deodorizer to clean the entire cage. But it doesn't seem to work. He ends up pissing everywhere and starts rattling the cage so we'll let him out to roam around the house.
My other bunnies are fine, they learned how to use the litter box within a day. It's just Thumper. I've been trying to get him to use the litter box for almost two months now... -.-"
He's very stubborn.