Has mama cleaned? I ask because that is a good indication of oxytocin levels post calving. A long strenuous labor can hinder oxytocin levels and in turn milk let down in dam. Additionally long labours sometimes make calves a little slower to open mouth and get to work, right idea but not making the right connections. In these situations we always give a bottle, usually just a litre, just enough to give mom a break, teach calf a little nursing skills and gives the calf nutrients but not too much so it will want to try again. Especially if we can't be there to watch we know it's had a bit to buy us some time for other things. If calf is weak we tube otherwise bottle every time on the first attempt. Sucking puts milk right into the abomasum where it go right to work warming calf etc and you bypass the rumin which is best. And after long labour, hard pulls we give a shot of oxytocin. Oxytocin is a prescription drug so vet relationship needed here in Canada. As for the wall in throat…I am not sure…if the calf swallows the bulb you are positioned right, sometimes a slight pull back, ever so slight, so bulb stays past that swallow point will often work. Your end can be up against the stomach wall. Additionally you may need to slightly unscrew your cap to create flow. Hard to say when not feeling what you are feeling but I know these were tips we gave our kids when they were learning. Last week we had a heifer calve and she was standing but calf not getting it. So got bottle after some time of not much success. He sucked only a cup from the bottle and seemed pooped so left him for a bit while I checked another. He got himself up again. Returned 10 minutes later he had it figured out - "open my mouth grab the teat get milk"!!