Just a thought, but what kind of floors do you have in the house? If it's a porous floor (unsealed wood, tile, carpet and padding) and you don't get out every last bit of urine and scent, he could still be smelling the urine and feel that it's okay to pee in the house.
Our male puppy kept peeing right in front of the door from the house to the deck, and once we ripped up the carpeting and replaced it, he didn't pee there anymore. He was about 18 months when we did that.