Mine does refuse sometimes - so I calmly wait a few minutes to see if he’ll eat, if not - fruit and plain yoghurt, with some porridge oats mixed it.
I should add, I’ve got into a routine now of giving him a larger lunch and mid afternoon snack as he was always getting too tired near dinner time - so for us his dinner consists of a boiled egg, either cucumber or avocado, cottage cheese and toast (or pasta/mash)
I can’t really offer any advice, we sometimes go through waves of not wanting dinner here as well. But I just wanted you to know your absolutely not failing him and you’re a brilliant mother xx