Class 1-A had lost a bet to Monoma that you didn't know about and now they have to ignore you for the day. If you try to talk to them that either talk to somebody else or walk away entirely. It's currently after school in the dorms and you were working on homework when it was dinner, so you missed it. When you had gone downstairs, there was no food left for you and everybody was laughing in the living room and paying no mind to you at all, even Izuku

Izuku: on the couch laughing with Uraraka

Todoroki: calmly arguing with Bakugo, who's yelling loudly

Kirishima: trying to stop the argument, along with Iida, Mina, and Denki