Hahns macaw not letting me touch or scratch his head.

I have had sun counure and an african grey both of which lived for 2 years each with me and I didnt have this problem with them. About a month ago I replaced my Grey for Hahns macaw cause of Down powder. he is hand reared and doesnt bite when out of cage. Steps up and down recieves treats, is on pellet diet. The problem is whenever i try to touch his head or anywhere he gets agressive and want to bite, otherwise he is a sweet bird. Can anyone help me out ?
Also, he dont wanna eat any Fruit or veggies, i just converted him from all seed to pellet diet. I really wanna scratch his head like I did to my conure and grey.

The bird is clearly telling you he's not ready for that interaction yet. Some parrots just don't like being pet even though they enjoy being handled. Even parrots that do like being pet should only be pet on the head as elsewhere on the body is very sensual and can encourage mating behavior, hormonal aggression, etc. As for getting your macaw to eat veggies, there are plenty of threads here on that already.

I'll be honest though, I don't think you'll get much advice posting that you gave away your African Grey after 2 years and now are struggling with your "replacement" bird. Using the language "replaced" just isn't indicative of someone who values their birds. :/ I wonder what happened to your sun conure? I hope you didn't "replace" that bird as well. It's not my intention to be rude but parrots just aren't items to be swapped out when they become inconvenient. Hopefully there's more to this story.

Im sure there is more to the story.He is focusing on his Macaw that doesn't wanna be pet which is normal because not all birds like being touched.So he's not gonna mention the whole story if the thread isn't about his African grey.I actually dont think the dust from greys is bad.I own cockatiels too and frequent bathing keeps the dust away.Anyway a Parrot is for life you cant just give them away for something silly as that I really hope there is more to this story.

You could teach your hahns to bow his head, then pair bowing his head with getting your finger closer. Then move on to touching but not petting. Then eventually petting.

Two years does seem to be a short time for a conure and an african grey.... although I know sun conures are loud and greys are dusty.