That's an awful long time to be crated, all day while you work, and all night while you sleep? He's probably become used to laying in his own waste
Maybe if you got and X-pen and put down some pee pads, along with his food and water,and toys, and then the crate inside that with the door open, he might start using the pads and just sleeping in his crate.
Good luck, I know it's hard, you just have to keep at it and try something new when you hit a dead end
