Please help, my son won’t eat. Anything. Ever. Unless he’s at his grandmas.

We offer snacks and full meals and he never wants anything. He will ask for something specific and I’ll make it and suddenly he doesn’t want it. Then he asks for something else and doesn’t want it… on and on and on. I’m tired of wasting food, I’m getting worried about him not eating, his grandma gets pissed if he’s not fed when I bring him over so I can go to work. We’ve tried having him help make it and it’s not even working doing that.

What could be going on and how to I get him to eat?! :(