I have had all sorts of calves and calve issues. Largely they are uneventful, but 1 of 10....and all beef mainly...so no BS
Have had many that will not take a bottle or any milk at all, the last couple were already about 250 plus lbs, I wrestled them for a bit, but they were used too mums teats, one sort of looked in a bucket, but, I just kept putting different feed and hay in front of them till they ate.....then gave them what they would eat.
Had a number of calves not interested in milk from bottle, but, after getting them sort of started, I let them get hungry, they would watch the others drink, and whinge, I would give them a bit, but, left them hungry....near all followed the others eventually, it is kinda funny, some of the most resistant became like crack heads and after milk at all cost.....they would still drink now no doubt.
I had about 2 in one group that only liked a bucket....yeah, sure, ok, I am sick of wrestling you....here is a bucket ! lol
So I have had 2 calves absolutely reject milk replacer altogether, no danger of starving as ate other feeds, had a couple sick, sorry guys, I tube fed for about 2 weeks, the last one I tube fed milk is as playful and strong as, but alas, 4 plus weeks behind..... TBH, I have tubed milk into quite a few, I see no drama, unless nearly dead, they actually drink on the tube and salivate etc....
They need the goodness from the milk imo, do not go too long with no milk.
I am patient, but if you have 20 animals to hand feed that are young, you cant spend 30 mins each, if it is by itself, not in a group, and you not been at it for over a week, then you just need to keep it up, if it has a physical impairment, or is ill, that changes everything, I would keep tubing milk, just not too much, keep pellets, chaff, and whatever else available to nibble on, some of mine have taken to pellet and chaff real well....last is, do you have a small hungry glutton you can put him with ?
One thing I know, and this applies to what I write, best not listen too others, had a number of people sell me calves saying they wont drink milk....mmm, yeah, right ! My oath they did !