Mine was like this! When we first got him he was weaned but we think the stress made him lose progress and he would not eat at all. We were worried he’s starve so tried to hand feed him formula and voila, he was eating! After a week or so of two feeds a day to get his weight back up, we ended up leaving him for the day and feeding him formula at around 4pm. He’d cry all day until he was around 4 1/2 months, when he eventually decided he had enough of formula and went on to seed (we’re still trying to get him on pellets and veggies though!). It was like a switch being flicked. One day he was crying for formula and the next he was completely eating all on his own. It’s irritating, I know, but persist and he will eventually wean himself when the time is right for him.