I feed my birds (other than my chickens (hens) -they have a more complicated diet since they lay every day) eat like my kids ate when they were little. New foods are usually looked at strangely or sometimes they just love it. Most few times they see it, they may take a taste and stay away the rest of the day. I introduced a lot in the beginning to figure out what everyone's favorites are. I just kept serving the new item into their bowels, plate, tray and cage until they tried it. Try cutting the fresh foods different ways. I had to chop, dice, figure, mash, puree until I figured out that they like things separate. Mine don't like chop (not yet anyway, I've tried 4 x, and it ended up all getting thrown out) but the veggies about half the size of their bodies and recognizable, they act like locusts! They don't like broccoli, cauliflower, carrots, etc., chopped fine. We make a pretend garden with the food, using the broccoli as bushes/trees, cherries, oranges, and other fruit into small shapes so they look like pretend flowers (in our minds, they actually look like pebbles) mixed young greens as the grass, then put toys on it. I also provide them all roundybrush crumble (not pellets since our birds are small and picky), Lafeber's avicakes, nutriberries, and a little seed but this counts for about 40-50 percent of their diet. Mine are definite millet junkies (I use it to train) but they also eat broccoli with gusto after having served and thrown out probably 8 heads of broccoli, same with cauliflower, strawberries, etc.
Keep trying! It's good for them and they need the dark leafy greens, oranges, purples (I head not rhubarb though) and cut, chop, whatever you can and try it on your little one. Let us know how it goes!