12 month old only eats breakfast

My boy has always been terrible with solids. Now he’s only eating 1 meal a day. He’s lost 200g in weight, and the health visitor wants us back so re weigh in a few weeks time. They said to just fill him with lots of dairy but with the ever loving fuck do I do when he’ll only eat breakfast?? I’ve tried leaving food out for him to graze on but he just moshes it into the floor. Ive resorted in giving him more milk as I’m terrified he’s going hungry.

What do I do??