Hello and congrats on your Harlequin, I love hybrids!!
Your macaw is starting to wean. As it's starting to refuse formula, it's now time to start presenting all sorts of different foods to him now -- bird-safe fruits, veggies, legumes, grains, pellets, etc. As time goes on you can also present nuts for them to start exploring with and using their beaks to break open. Try to softer fruits and veggies first, there are so many out there, some birds develop a favorite, maybe he just hasn't found one he likes yet. There are lots of different combinations you can try to entice your bird to eat these foods instead of the morning feeding. Present these foods at your normal feeding am time. Over time, if all goes well he should stop eating formula altogether and eat the food you give him.