Yes, they stop eating if they have a blockage. If they have a blockage, or stop eating or stop pooing, it is considered a medical emergency and you really are supposed to go to the vet right away. If for some reason you can't get to a vet right away and if you don't see your rabbit drinking, dehydration is a real danger because usually if they aren't eating they probably aren't drinking either. A rabbit can't move a blockage through its intestines if it is dehydrated, so with my rabbits I always syringe a few tablespoons of water/electrolytes into them (they are around 2 kg so a tablespoon per kg) if I suspect their gut isn't moving food through. Also, If a blockage is suspected you are not supposed to syringe food as this might make the blockage worse. Offering leafy greens with water on them is a good idea if they are still eating. But I would get the rabbit to the vet as soon as possible.