Unfortunately, some bunnies like to pee on soft things. I have 2 of those. Is it possible to move his play area to a different room? Or create a fence that he can’t reach the couch? I’v heard of people placing a litter box on the couch. Don’t know if that will work. Also, as much as I have read about this – rabbits are not like dogs. You can’t scold them and put them in time-out like we do with dogs. Punishment is shown to be a poor training method in dogs, and just doesn’t work in rabbits. Positive reinforcement works better. But since it is impossible to apply this when your rabbit does not pee on the couch, I honestly think you have 2 options. Try the litter box on the couch, (which I wouldn’t do coz I don’t want flicked out hay/poop on my couch), or move the play area/find a way to restrict the rabbit’s access to the couch.
Maybe others have had a different experience than me and can offer other suggestions…