My rabbit is lying down, not eating, and pressing his belly. What now?

Hello. It sounds like your rabbit may have signs of gastrointestinal stasis, which means the GI tract has slowed down, usually as a result of a rabbit that stops eating. Rabbits will stop eating for a number of reasons - their teeth may be overgrown, their tooth roots may be infected, they could also have any other systemic disease (respiratory, urinary, infection, etc). As you can see, the causes are many and its impossible to say what is the underlying cause for sure without an exam and testing (usually radiographs, blood work, etc). Regardless of the cause, GI stasis is potentially fatal if left untreated. Therefore, I would urge you to get veterinary care ASAP. In the meantime, syringe feed Hobie with a liquid hay diet, ideally Oxbow herbivore critical care if you can get some, or soak the hay pellets in warm water to make a slurry. The best thing to keep the GI tract healthy is fiber and hydration, so hay is the foundation of health. I see in the first picture a pellet mix with maybe some oats, corn, and/or seeds mixed with the pellets. This is not an appropriate diet for rabbits as they are selective feeders and usually pick out the concentrates. These pellet mixes significantly increase the incidence of dental disease and obesity. I recommend a 100% timothy hay pellet, ideally Oxbow brand. Feed 1/4 cup timothy hay pellets, free choice grass hay, and 2 cups fresh greens a day with fresh water available in a bowl and sipper.