Hello everyone, we're having this situation for the second time in a m…

Hello everyone, we're having this situation for the second time in a month, can you explain what could be the reason? We're on IV. The daughter hasn't drunk formula or eaten all day, but if she was hungry, she would have let us know. Today she drank 120 ml of formula and that's it ??‍♀️ I prepared mashed potatoes and soups all day long, but nothing. What could it be?