Help please

Hiba

My baby is 12 month old, we switched him to neocate junior with prebiotics vanilla flavour due to CMA, since then he has stopped taking feed, he will only drink while sleeping orherwise he wont, he has gone with feed for 16 hours, he will drink water but not drink milk if he is not sleeping, because of this he has become very fussy and cranky, he doesnt really eat anything these days also, anyone who has gone through this please