What is his age? Even rabbits that litter train when very young can forget that training with the onset of hormones. If your guy is hormonal, it can be an uphill battle to expect him to go in the litter box. Once he's neutered and hormones have dissipated, rabbits typically train themselves. All we need to do is to provide the right set up and they will go in the box of their own accord. I'm afraid you may need to be patient and wait it out until he's neutered.How long does it usually take for them to start using the litter box??.