A rabbit that stops eating is an emergency, and the clock is about 12 hours

This is the single most important thing to know if you have a rabbit, and it's the thing new owners find out too late. Rabbits are hindgut fermenters and the gut has to keep moving more or less constantly. When it slows or stops, which vets call GI stasis or ileus, gas and the wrong bacteria build up in the cecum, it gets extremely painful, and the whole thing feeds itself, because a rabbit in pain won't eat and not eating slows the gut further. The House Rabbit Society is blunt about the timeline and they're right to be. If your rabbit has stopped eating or stopped producing droppings for 12 hours or more, treat it as an emergency and get to a rabbit savvy vet. Left alone it can kill within a day or so after that. What you're watching for besides not eating: no poops at all, or suddenly tiny ones, sometimes strung together with fur. Sitting hunched and very still. Teeth grinding, which in a rabbit is a pain signal and not the contented purr people assume. Cold ears. A belly that feels hard or makes loud gurgling noises. Also worth saying out loud, rabbits can't vomit. Whatever goes in has to keep moving forward, which is a big part of why this goes bad so much faster than the same situation would in a dog. Two things to do now rather than then. Find the nearest vet who actually sees rabbits and save the number, because a lot of general practices don't and you'll burn real hours on the phone finding that out. And learn what your rabbit's normal litter box output looks like. That pile is your early warning system and it's free.