Sometimes ekkies become bored with the food they eat & this can stop them from eating. Keeping their meals & food interesting will prevent this. You can do this by offering skewers, foraging toys, hiding food throughout their cages & play gyms, making all kinds of recipes & shapes.
You can also try adding a little peanut or almond butter to the foods they don’t particularly like to get them to try the new food. In most cases once they get the first taste of the new food they will be willing to eat it.
Hang leafy green veg like bok choy, kale etc...on their perches & branches. Hang edible flowers or safe foliage.
Allow them to join you for a meal. This can often encourage them to eat since they enjoy eating with the family & are curious about what we humans eat.
Supply your bird with foraging toys & ideas to get him interested in eating. You can visit the Parrot Enrichment Page to get lots of foraging tips & ideas.