Depending on what the rabbit has eaten, food will take anywhere from 5 to 20 hours to pass through the digestive tract. So yes, 5 days with no poop is an emergency situation. I would stop force feeding for now and get her back to the vet right away. Force feeding makes sense when the stomach is empty as it helps the digestive tract to start working again. In this case, after 5 days of force feeding and no poop, her stomach must be filled to the brim. Forcing more food down her throat won’t do any good at this point, it will only cause her pain and could actually cause her stomach to rupture (be careful with the tummy massages). Get her back to the vet and have them do another x-ray to see where the food is/if it’s moving through the digestive tract at all.
I also want to echo what Bunny House said. Is your vet bunny savvy? It might be a good idea to get a second opinion from a rabbit savvy vet. This is definitely an emergency. And yes, baby gas drops can help a lot.