Thanks jerseygirl! Sooooo glad you are here!
I have had to do litter training refresher courses – usually when something sets them off. A petsitter, the cat got into their area – they..Jack doesn’t like him in his space. Usually if I let it go on for too long, it takes a longer time to retrain, so if they’ve been like this for awhile, be prepared that it could take a month if they are stubborn.
Also, many times rabbits have poo more during part of the day than the others. For example, Jack usually poos in the evening and throughout the night because that is when he eats the most. So if you can figure out their poop schedule and then be there when they are pooping or peeing in the wrong place and catch them in the act and get them to their litterbox – that will have the fastest impact. I also cut treats into tiny itsy bitsy pieces and scatter it throughout the hay (usually opposite of the corner that that they normally pee in in the box) This helps entice them in too.
Jersey is so right about a box being too clean too or too dirty. You can find what your bunnies prefer. Jack prefers to have poop and pee in there. If it is totally clean, he won’t go in there.(So when I clean the box, I always put back some of the urinated/poo litter (not much, just like a 1/3 cup) Rucy, however, was just the complete opposite. So I kept two boxes – one to suit her habits, and one to suit his. Of course, Jack always got into Rucy’s too once she had gone in there, but I just was much more diligent about her box. Scooped up the poo/pee every day in her box.