Honestly I'm shocked that it only took 2 weeks for you to get him to let you put him on it, and that he's not constantly chewing at it, as it usually takes most birds months and months to over a year just to be able to get it on them, and even then they typically chew and chew and chew on it the entire time they're wearing it...
So there is absolutely nothing at all wrong with your bird, you just took the harness-training way too quickly, and he's just extremely uncomfortable, anxious, and upset about wearing it, as it's just too soon to keep it on him for any long periods of time, and by that I mean for a few minutes a day. You just didn't know and that's understandable, but now that you do know you need to hit the brakes and SLOOOOW DOWN!
Birds don't naturally wear clothing or have anything touching them or anything "around" them like a harness, so it is going to take a while before he's not scared of the harness and is actually okay with accepting it and wearing it...A lot of the time with a very sweet, hand-tame bird that doesn't mind being handled, you actually are able to force it on them without a fuss, but that doesn't take away their fear of it. They let you put it on them all at once because they are very tame, but once it's on them they're terrified of it and totally uncomfortable, and that's where you bird is at right now...He let you put it on him very quickly, but he's scared to death of it and is very uncomfortable wearing it...
So what you need to do is just put it on him once a day, every day, for only a few minutes, like 5 minutes tops, and as soon as you get it on him you need to give him a special treat, whatever his favorite treat is...Then talk to him while he has it on, make him feel as comfortable as he can feel, and if it's warm enough outside then take him outside in it right after putting it on him so he can see that the harness means he gets to go outside...Then after 5 minutes take it off of him and give him another treat and more verbal praise...And that's it until the next day...And each day extend the time period he wears it by a few minutes, and be sure to give him a treat as soon as you get it on him and then another after it comes off, and some in between while he's wearing it, along with lots of verbal praise....Each day add a minute or two to the time he wears it, and eventually he will get used to wearing it and he will also associate it with treats and going outside. Eventually he'll be fine in it all the time, but 2 weeks is WAY TOO SHORT a time period to just put it on him and expect him to totally accept it, because it's totally unnatural for them and right now the reason he is quiet and not moving when he has it on because he's terrified of it.
Be patient and go at HIS PACE with wearing the harness, not your pace. It will happen, but you can't force it, it must happen very slowly and gradually over-time, just like anyone getting used to anything new and abnormal for them to be wearing. It's a marathon, not a sprint...