What a great video! Kizzy is such a character!
As for the harness, don't be discouraged. Setbacks are par for the course with harness training, but she'll bounce back.
I'm glad to hear you say that.

I had arrived at the same conclusion, but it's nice to hear someone with experience encourage me to keep at it. We'll work on desensitization again tomorrow and skip putting it on her again.
How lucky I was to get such an intelligent, sensitive young Amazon! She's testing me to see how much bite pressure she can get away with. I've tried various methods, but so far the most successful is a loud, "No!" followed by a long glare. Yes, I was worried that yelling might be rewarding her, but she's a sensitive bird, so I think she understands she's doing something I don't like and wants to comply. The glare actually upsets her a little, which makes me feel bad even though it's probably necessary. I know I have predator eyes, so I reserve the glare for serious offenses. After the glare, she sometimes makes whining noises as if to say, "Do you still love me? I need to know right now that you still love me!" Once she's properly contrite, I forgive her and she's gentle for awhile. Of course, she usually ramps it up again. She can't help being rambunctious because she's a young Amazon, full of insane amounts of silliness and energy.
She's teaching me, too. Sometimes when she gets silly, I'm the one who plays too rough. If I accidentally hurt her or make her feel uncomfortable or do something stupid, I feel I deserve any bite coming my way. Yes, it's always the human's fault.
I've been around a lot of parrots. I worked at two pet stores (AKA hell holes, but I tried to make them better) and raised CAGs and Senegals. This is an exceptionally intelligent bird. I didn't get a CAG because I felt greys might be too intelligent, sensitive and demanding for me. Instead, I got an Amazon that borders on CAG intelligence, sensitivity and behavior.

Surprise! It's been a challenge and will continue to be a challenge, but I welcome it. I need the stamina to meet this challenge. I'll certainly do my best.