To be honest, my little one was the same when she first started, she went on hunger strike. The staff were calm and persistent and would take her to a quiet area and give her milk. She just got better once she relaxed, got to know the staff and now she loves nursery and the food. They would make us aware, but just tell us not to worry and they would keep trying with her. I’m not sure what else you can do other than wait for them to settle!
My little girl started at 9 months and was the same with her food. By week 2 she was completely different and eating. Just give them time to adjust and soon will be loving it.
Can they not let you take on a packed lunch?